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LIBRARY OF CONGRESS 
RECEIVED 

MARI-1921 

DOCUMENTS DIVISION 







JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 


The following papers which enunciate, respectively, the principles 
that will govern the joint action of the Army and Navy in coast 
defense, the action of the Navy in coast defense, the system of coast 
defense to be employed by the Army, and the procedure to be fol¬ 
lowed by the Army in the preparation of defense projects and plans, 
are published, upon the recommendation of the Joint Board, for the 
information and guidance of all officers of the Army and Navy: 

Part I.—Joint Army and Navy action in coast defense. 

Part II.—Action of the Navy in coast defense. 

Part III.—A positive system of coast defense. 

Part IV.—Defense projects and plans. 

Newton D. Baker, 

Secretary of War. 

Josephus Daniels, 
Secretary of the Navy. 


3 







Part I. 

JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 


The following principles will govern the joint action of the Armj 
and Navy in coast defense: 

1. Coast defense includes dispositions and operations having 
for their object the repulse of a hostile attack upon any portion of 
the seacoast of the continental United States, the Panama Canal, 
or the insular possessions, or upon naval vessels or merchant ship¬ 
ping in or off harbors or in coastwise sea lanes. 

2. The elements which enter into coast defense comprise— 

(a) Naval forces. 

I. The United States Fleet, other fleets and detach¬ 
ments. 

II. The naval coast defense forces. 

III. The Marine Corps. 

(b) Military forces. 

I. The harbor defenses. 

II. The mobile forces of the Army. 

3. The missions and functions of the naval forces in coast defense 
are: 

I. The United States Fleet is a mobile force free to move from 
area to area in accordance with the strategic situation, to operate 
against the main or most dangerous enemy forces and all enemy 
forces within striking distance for the purpose of gaining and main¬ 
taining the command of vital lines of sea communications. Such 
a command, when won, insures freedom of movement on the Sea to 
our vessels and denies such freedom of movement to enemy vessels, 
thereby protecting our coasts from attack. Other fleets or detach¬ 
ments may be organized in secondary areas for the control of the 
sea communications within those areas in which only small detach¬ 
ments of enemy fleets may be expected. 

II. The naval coast defense forces are usually assigned to naval 
districts for the purpose of controlling the sea communications 
therein. The limits of the naval districts are considered to extend 
to seaward so far as to include the coastwise sea lanes. It is a 
policy of the Navy Department that naval vessels and aircraft as¬ 
signed to naval districts in the continental United States shall be 
kept at a minimum so that all naval vessels which will add to the 
power of the United States Fleet may be assigned to it. The naval 

5 



6 JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 

coast defense forces are adjuncts to and operate in connection with 
such fleets or detachments of fleets as are based in their general 
locality. 

III. The Marine Corps may, in exceptional cases required by the 
national interest, be used fol* coast defense in the continental United 
States and insular possessions in the way described for the Army. 
The most important function of the Marine Corps is to seize and 
hold temporary advanced bases in cooperation with the fleet and to 
defend such bases until they are relieved by the Army. In such 
cases the Marine Corps detachments will have, in general, a mission 
in coast defense similar to that for Army garrisons of insular pos¬ 
sessions. Their methods of defense will generally correspond to the 
principles laid down herein for the Army, as far as they apply to the 
defense of advanced bases. This coordination of the Army and 
Marine Corps in coast defense is important, as it wfill preserve the 
mobile character and facilitate the relief of marine advanced base 
detachments by permanent Army garrisons when’the line of com¬ 
munications has been made secure. 

4. The missions and functions of the military forces are: 

I. The harbor defenses. —Harbor defense includes dispositions and 
operations for the defense of limited portions of the seacoast, or¬ 
dinarily confined to important harbors. Such dispositions usually 
include fixed armament,' mobile armament, controlled submarine 
mines, and the troops and accessories required for their employment 
and local defense. Harbor defenses have distinct missions over the 
sea and the land areas covered by their armament: 

(1) To deny the enemy possession of the position and its facili¬ 

ties. 

(2) To prevent destruction or serious injury by bombardment 

of the harbor utilities. 

(3) To provide an area off the harbor entrance in which 

naval vessels and merchant shipping will be protected 

as far as possible against all forms of enemy attack. 

II. The mobile forces of the Army.—The mobile forces of the 
Army include combat troops of all arms and have the mission in coast 
defense of operating against enemy forces making attacks on the sea- 
coast or operating in the coastal area. 

5. The usual composition and organization of the naval forces 
are:’ 

I. The United States Fleet or other fleets . 

(a) Battleship division: Four battleships. 

(b) Battleship squadron: Two battleship divisions. 

(c) Battleship force: All battleship divisions or squadrons of 

the fleet. 

(d) Cruiser division: Four cruisers or light cruisers. 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 


7 


I. The United States Fleets and other fleets— Continued. 

(e) Cruiser squadron: Two cruiser squadrons. 

(/) Cruiser force: All cruiser divisions or squadrons of the 
fleet. 

(g) Destroyer division: Six destroyers. 

(h) Destroyer squadron: Three destroyer divisions, one light 

cruiser (flagship), one destroyer tender. 

(i) Destroyer flotilla: Three destroyer squadrons, one light 

cruiser (flagship). 

(j) Destroyer force: All destroyer squadrons or flotillas of 

the fleet. 

{Jc) Submarine division: Three to 10 submarines of the same 
type, one submarine tender. 

(1) Submarine force: All submarine divisions of the fleet. 
(rn) Air force: Aircraft carriers and tenders with attached 
airplanes and seaplanes, rigid dirigibles, kite balloons. 

( on) Mine force: Minelayers, light minelayers, and mine 
sweepers. 

( o ) Train: Oilers, colliers, repair ships, store ships, hospital 

ships, etc. 

(p) Naval Transportation Service: Colliers, oilers, store 

ships, transports, etc. 

(g) Advanced base forces (Marine Corps) : Infantry, machine 
guns, field artillery, fixed batteries, controlled mines, 
antiaircraft batteries, searchlights, aviation squadrons, 
and auxiliary services. 

II. The naval coast defense forces. 

(a) Naval Communication Service: Radio stations, radio 

compass stations, telegraphs, telephones, lookout system. 

(b) Patrol divisions: Patrol vessels. 

(c) Naval air stations: Scouting planes, patrol planes, bomb¬ 

ing and torpedo planes, nonrigids, and kite balloons. 

(d) Mine divisions: Mine layers and sweepers. 

(e) Submarine divisions: Three to 15 submarines. 

III. Marine Corps. 

(a) Local defense forces: Infantry, machine guns, and such 
light fixed or mobile guns as may be useful for purely 
local defense without duplicating the Army plans for 
coast defense. 

G. The Composition and organization of the military forces are : 

I. The harbor defenses. 

(a) Fixed armament: Guns, howitzers, and mortars mounted 
in permanent emplacements, incapable of being moved 
or readily transferred and designed to fire over limited 
areas. The fixed armament is classified as major, inter¬ 
mediate, and minor, depending on the caliber. 


8 JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 

I. The harbor defenses —Continued. 

1. Major armament consists of 8,10,12,14, and 16 inch 

guns, 16-inch howitzers, and 12-inch mortars. 

2. Intermediate armament consists of 5 and 6 inch 

guns. 

3. Minor armament consists of 3, 4, and 4.7 inch guns. 

(6) Mobile armament: Guns, howitzers, and mortars on mov¬ 
able mounts, capable of being readily moved or trans¬ 
ferred. The mobility possessed by armament of this 
class is limited by the type of mount and may be classi¬ 
fied as strategical and tactical mobility. For example, 
all types of railway armament possess strategical mo¬ 
bility, but the tactical mobility of certain types is 
limited, due to the characteristics of the mount. The 
mobile armament is classified as primary and secondary, 
depending on the caliber. 

1. Primary armament consists of 12 and 14 inch guns, 

16-inch howitzers, and 12-inch mortars on rail¬ 
way mounts. 

2. Secondary armament consists of 7, 8, and 10 inch 

guns on railway mounts, and 6-inch, 155-milli¬ 
meter, G. P. F., 7-inch guns, 8 and 9.2 inch 
howitzers, on caterpillar mounts or tractor 
drawn. 

( c ) Antiaircraft armament: Three and 4.7 inch guns, on fixed 

and mobile mounts. 

(d) Submarine mines: Shore controlled mines, mine planters, 

and accessories. 

(<?) Coast defense aircraft: Observation units, lighter and 
heavier than air types. 

(/) Accessories: Searchlights, coast defense radio, fire-control 
installations, etc. 

(<y) Organization: The elements above indicated are organized 
at present as follows: 

1. Gun defense: (1) Battery commands consisting of 
one or more guns, howitzers, or mortars, com¬ 
manded directly by a single individual, together 
■with all structures, equipment, and personnel 
necessary for their emplacement, protection, and 
service. (2) Fire commands consisting of two 
or more battery commands, the additional fire- 
control stations and accessories and the person¬ 
nel assigned thereto. The senior officer present 
for duty is the fire commander. 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 9 

I. The harbor defenses —Continued. 

2. Mine defense: Mine commands consisting of such 

portions of the mine defense as can be controlled 
advantageously by a single individual. The senior 
officer present for duty is the mine commander. 

3. Fort commands consisting of all the means of sea¬ 

ward and landward defense, including both per¬ 
sonnel and materiel, located at any coast fort. 
Unless otherwise directed by the Secretary of 
iWar, the senior coast artillery officer present for 
duty, other than the coast-defense commander, 
is the fort commander. 

4. Coast-defense commands consisting of a group of 

fort commands provided for the defense of a 
harbor or point of the coast. The senior coast 
artillery officer present for duty is the coast- 
defense commander. 

Our harbors, if undefended, would be the weakest points in our 
line of defense, and since they are also of greatest value to the enemy 
it becomes important that these points be strengthened by more com¬ 
plete fortifications than other parts of line. 

II. The mobile forces. 

(a) Infantry division: Combat unit consisting of— 

One division headquarters. 

Two Infantry brigades. 

One Field Artillery brigade. 

Auxiliary and special division troops, including— 
Engineers. 

Air Service. 

Medical. 

Signal. 

.Military police. 

Trains. 

(b) Army corps: Consisting normally of— 

One corps headquarters. 

Three Infantry divisions. 

Auxiliary and corps special troops, including— 
Artillery. 

Engineers. 

Air Service. 

Antiaircraft. 

Medical. 

Signal. 

Military police. 

Trains. 


11313 °— 2 ( 


10 JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 

II. The mobile forces —Continued. 

( c) Field army: Consisting normally of— 

One army headquarters. 

Three army corps. 

Auxiliary and army special troops. 

Tables of Organization published by the War Department show in 
detail the distribution of personnel and armament in the above or¬ 
ganizations. 

III. Defense sectors. —For command and other purposes the sea- 
coast areas are divided into sectors, which usually include defended 
and undefended areas. The limits of defense sectors are prescribed 
by the War Department. According to the foregoing, a defense sec¬ 
tor comprises the entire sea frontier within its limits, of which the 
harbor defenses are strong points and not isolated points to be de¬ 
fended. A major sector is a sector of such magnitude as to require a 
sector reserve of a division or more and not susceptible of reinforce¬ 
ment except from the general strategical reserve or by transfer from 
another sector. A minor sector is a sector of such magnitude that the 
sector reserve may be less than a division and yet so situated as to 
make inexpedient to organize it as a subsector. A minor sector is 
not susceptible of reinforcement except from the general strategical 
reserve or by a transfer from another sector. 

A subsector is a part of a major or minor sector, but forming a 
separate tactical command, with its own reserve, under the sector 
command and susceptible of reinforcement by the sector reserve. 
Corps areas and oversea departments will constitute defense sectors, 
similarly named. Corps area and department commanders thus be¬ 
come the “sector commanders” and as such are responsible for the 
defense of their respective sectors. 

7. In general, attacks on the seacoast can be divided into two 
classes: 

( a ) Unsupported attacks. 

(b) Supported attacks. 

Unsupported attacks are surprise attacks or raids made by light 
enemy forces for the accomplishment of a minor mission. 

Supported attacks are those in which the forces which carry out 
the actual attack are escorted, assisted, or supported by considerable 
naval forces in the attempt to carry out an important mission, which 
will affect the entire campaign. 

8. There are the following eight general forms of attack on the 
seacoast, each of which may be made as either unsupported or sup¬ 
ported attacks: 

A. Aircraft attacks on seaports. 

B. Mine-laying attacks off the seacoast. 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 


11 


C. Torpedo, bombing, and gunfire attacks on vessels oil the 

seacoast. 

D. Torpedo fire into seaports. 

E. Blocking attacks on seaports. 

F. Bombardment of seaports by naval vessels. 

G. Penetration into a harbor or water area by naval vessels. 

H. Landing attacks. 

9. The following types of enemy vessels or enemy forces may be 
used to make attacks on the seacoast or to assist or support those 
actually making the attack: 


Battle squadrons. 
Cruisers. 

Destroyers. 

Submarines. 

Minelayers. 

Light minelayers. 
Mine-laying submarines. 
Mine sweepers. 

Landing parties. 
Aircraft carriers. 


Fighting planes. 

Torpedo and bombing planes. 
Observation planes. 

Aircraft tenders. 

Scouting planes. 

Rigid dirigibles. 

Battleships, second line. 
Blockships. 

Expeditionary forces. 


10. In the case of unsupported attacks our forces must obviously 
operate against the enemy force actually making the attack, thus 
frustrating it, if our operations are successful. In the case of sup¬ 
ported attacks our forces have the choice of operating against either. 

(a) The enemy forces actually making the attack, which, on 

account of the hazardous nature of the duty, are usually 
composed of small and unimportant vessels. 

( b) The enemy forces supporting or assisting the attacking 

force, which are usually composed of larger and more 
valuable vessels. 

In the first case we may sink or damage unimportant naval vessels, 
and by doing so frustrate the attack and prevent the enemy from in¬ 
flicting damage on the objectives of their attack. 

In the second case we may sink or damage important naval vessels, 
but we can not frustrate the enemy immediate attack, the objectives 
of which may be damaged. 

That course of action should be pursued which it is estimated will 
result in the greatest advantage for us in the conduct of the com¬ 
bined Army and Navy campaign. 

11. The primary functions or missions of the various arms, 
branches, and types of the Army and Navy forces are given in the 
following paragraphs. These functions are assigned for the usual 
conditions and do not prohibit the use of the arms, etc., on other mis¬ 
sions dictated by the actual situation. The fact that the function 


12 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 


given to certain arms, etc., in coast defenses is that of operating 
against enemy forces attacking the seacoast does not mean that all 
such arms, branches, and types are necessarily essential for the defense 
of any particular section of the coast; the functions or missions are 
stated so that such types, branches, and arms, if assigned, may be 
used in accordance with an accepted doctrine for their employment. 

12. The primary missions or functions of naval forces—whether 
attached to the United States Fleet or the naval coast defense forces— 
in coast defense are, in probable order of contact with the enemy: 

(a) Rigid dirigibles. —To locate and report enemy forces ap¬ 

proaching or operating off the coast, particularly where 
great cruising endurance is required. 

(b) Naval Communication Service. —To receive and forward 

reports of enemy forces approaching or operating off 
the seacoast, and to receive and forward reports from, 
and transmit instructions to, all our forces, active or 
passive, and to maintain liaison with all friendly ac¬ 
tivities. 

(c) Scouting 'planes. —To search for, locate, and report enemy 

vessels and, in case of submarines, to attack them, to 
bomb enemy surface craft during darkness, low visi¬ 
bility, or other favorable conditions. 

(d) Patrol planes. —To search for, locate, and report enemy 

vessels and, in case of submarines, to attack them; to 
bomb enemy surface craft during darkness, low visi¬ 
bility, or other favorable conditions; to escort naval 
and merchant vessels and attack enemy submarines en¬ 
countered; to search for enemy anchored mines, when 
water is clear enough for them to be seen. 

(e) Nonrigid dirigibles and patrol vessels. —To search for, lo¬ 

cate, and report enemy vessels and in the case of sub¬ 
marines, to attack them; to escort naval and merchant 
vessels and attack enemy submarines encountered. 

(/) Submarines. —To search for, locate, and attack enemy ves¬ 
sels and dirigibles, making such reports as will not in¬ 
terfere with the effectiveness of their attack. 

(g) Destroyers. —To search for, locate, and attack enemy ves¬ 
sels, those having greatly superior gun power being 
attacked during darkness, low visibility or other favor¬ 
able conditions; to escort naval and merchant vessels, 
attacking enemy vessels encountered, those having 
greatly superior gun power being attacked during dark¬ 
ness, low visibility or other favorable conditions; to 
attack all enemy vessels, when reported by other craft, 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 13 

those having greatly superior gun power being attacked 
during darkness, low visibility, or other favorable con¬ 
ditions. 

(h) Cruisers. —To search for, locate, and report enemy ves¬ 

sels, attacking those having approximately equal or 
inferior gun power; to escort naval and merchant ves¬ 
sels, attacking enemy vessels encountered which are 
approximately equal or inferior in gun power; to at¬ 
tack enemy vessels reported by other craft, when the 
enemy vessels are approximately equal or inferior in 
gun power. 

(i) Torpedo and bombing planes. —To attack all enemy ves¬ 

sels reported by other craft, taking advantage, where 
possible, of low visibility. 

(j) Mine layers and light mine layers. —To lay fields of con¬ 

tact mines immediately before enemy attacks in limited 
areas through which enemy forces are expected to pass; 
such fields should not limit the activities of our naval 
and military forces. 

(A*) Mine sweepers. —To sweep such channels as are necessary 
for our naval forces and merchant shipping and to clear 
mine fields laid by the enemy when they are encountered 
or reported. 

(1) Battle squadrons. —To operate against enemy capital 
ships or other forces as required by the actual situation. 
13. The primary missions or functions of the military forces in 
coast defense are as follows: 

(a) Intelligence Service. —Reports all enemy forces approach- 
* ing or operating off the seacoast. 

( b ) Air Service. 

1. Pursuit planes attack all enemy aircraft operating over 

and off the seacoast, and enemy landing parties; pro¬ 
tect Army and Navy aircraft against enemy aircraft. 

2. Bombing planes attack all enemy vessels off the seacoast 

and enemy landing parties. 

3. Observation planes assist in directing the fire of bat¬ 

teries, particularly when firing at long range. 

4. Observation balloons assist in directing fire of batteries 

at all ranges. 

5. Dirigibles assist Intelligence Service; assist in direct¬ 

ing fire of batteries, particularly when firing at long 
ranges; attack enemy vessels off the seacoast and 
enemy landing parties. 


14 JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 

( c) Harbor defenses. 

1. Fixed armament attack all enemy forces within effec¬ 

tive range, by day or night. 

2. Mobile armament supplement the fire of fixed arma¬ 

ment and attacks suitable targets within effective 
range by day or by night. 

3. Antiaircraft armament attack all enemy aircraft 

within effective range and by its fire keep enemy air¬ 
craft outside of effective range of important targets 
for their bombs, torpedoes, and machine-gun fire. 

4. Mine defenses close harbor entrances to enemy vessels 

and deny specified areas to enemy vessels. 

5. Searchlights search for and illuminate targets for all 

of the above elements. 

(d) Mobile forces. —The mobile forces are charged with the de¬ 

fense of the several beach positions in the intervals be¬ 
tween the harbor defenses. These positions are organ¬ 
ized for defense in accordance with the principles stated 
in Appendix II, “A Positive System of Coast De¬ 
fense.” 

14. When an enemy attack on the seacoast is made, the senior 
naval officer within the limits of the naval district or districts in 
which the attack is being made, whether commanding a district or 
a detachment of the fleet, will assume the strategical direction of all 
naval forces within the district or districts. 

15. The senior naval officer afloat in the area in which the attack 
is being made, whether attached to the fleet or a district, will as¬ 
sume the tactical direction of all naval forces in contact with the 
enemy. 

16. Army sector commanders are responsible for the defense of 
the sectors and for the initial distribution of the troops allotted to 
sectors. The senior local Army commander in any subdivision of a 
sector is responsible for the tactical dispositions or operations of the 
military forces against enemy attacks of whatever nature. 

IT. Cooperation between Army and naval officers directing op¬ 
erations against enemy attacks will be governed by the following 
principles: 

(a) When an enemy force of a strength greatly superior to 
that of the naval force available for use against it ap¬ 
proaches the coast, the naval officer will inform the 
Army officer of the situation and shall assume that the 
Army has a paramount interest in the operation and 
shall coordinate the operations of the naval forces with 
those of the military forces. 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 15 

(b) If, however, the conditions are such that the enemy is, 

or can be, engaged by a naval force approximating in 
strength that of the enemy, the Army officer shall be 
so informed and shall assume that the Navy has a para¬ 
mount interest in the operation and shall coordinate 
the operations of the military forces with those of the 
naval forces. 

( c) In the application of these principles, it is assumed that 

both the Army and Navy have forces suitable for 
operating against enemy attacking forces; one service 
obviously could not be given a predominating interest 
in frustrating an enemy attack, if it did not have avail¬ 
able forces which were suitable for operations against 
the attacking forces, even though the other service were 
greatly inferior in strength to the attacking forces. 

18. The best assurance of effective cooperation between the Army 
and Navy commanders within a given region will be found in co¬ 
operation in the preparation of defense plans in time of peace: In¬ 
telligent work of this character will result in the determination of 
the more probable situations likely to arise and in advance agree¬ 
ments upon plans of joint action for each such situation. 

The principal responsible subordinates and staffs must be informed 
of such plans and conform their peace organization and training 
thereto. 

19. Any instructions for cooperation between officers of the two 
services must fail of complete effectiveness unless the cooperation is 
brought to its logical focus in the offices of the Secretary of the 
Navy and the Secretary of War. 

20. To obtain this cooperation the Joint Board was reorganized 
in 1919 with the following members: 

Chief of Staff. 

Director Operations Division—General Staff. 

Director War Plans Division—General Staff. 

Chief of Naval Operations. 

Assistant Chief of Naval Operations. 

Director of Plans, Naval Operations. 

21. The Joint Army and Navy Board takes cognizance of questions 
referred to it by proper authority, involving joint action of the Army 
and Navy and joint Army and Navy policy relative to the national 
defense. It also has the duty of originating consideration of such 
subjects when in its judgment necessary, and is responsible for recom¬ 
mending to the Secretary of War and the Secretary of the Navy 
jointly whatever it considers essential to establish the sufficiency and 


16 JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 

efficiency of cooperation and coordination of effort between the Army 
and the Navy. 

22. In order to provide an agency for detailed investigation, study, 
and development of policies, projects, and plans relative to the na¬ 
tional defense and involving joint action of the Army and Navy, the 
Secretary of War and the Secretary of the Navy organized a Joint 
Army and Navy Planning Committee, consisting of: 

(1) Three or more members of the War Plans Branch, War 

Plans Division, General Staff, to be designated by the 
Chief of Staff. 

(2) Three or more members of the Plans Division of Naval 

Operations, to be designated by the Chief of Naval 
Operations. 

The Joint Army and Navy Planning Committee investigates, stud¬ 
ies, and reports upon questions relative to the national defense and 
involving joint action of the Army and Navy referred to it by the 
Joint Army and Navy Board. It also has the duty of originating 
consideration of such subjects when in its judgment necessary. The 
members of this committee are authorized to consult and confer 
freely on all matters of defense and military policy in which the 
Army and the Navy are jointly concerned, and this joint work is 
considered as their most important duty. 

23. It may often be found practicable and desirable, especially 
where an army corps area or department headquarters and naval dis¬ 
trict headquarters are in the same locality, for the two commanders 
concerned to organize a joint planning committee for the purpose of 
coordinating the plans and operations of the corps area or depart¬ 
ment and the naval district. 


Part II. 

ACTION OF THE NAVY IN COAST DEFENSE. 


THE UNITED STATES FLEET. 


The mission of the fleet is to gain the command of the sea by opera¬ 
tions against enemy naval forces. These operations usually give 
efficient protection to the seacoast. The protection can be afforded in 
several ways: 

1. By occupying a position in enemy waters and operating 

offensively. 

2. By occupying an advanced position and operating on the 

offensive defensive against enemy forces approaching our 
coast. 

3. By occupying a position on our coast and operating on the 

offensive defensive against enemy forces approaching it, 
denying by local defense our advanced positions to the 
enemy. 


Naturally the most satisfactory course will be for the fleet to occupy 
a position in enemy waters and to operate offensively against the 
enemy forces. If our fleet is exerting decisive pressure in enemy 
waters by attacking enemy ports, by enforcing a strict blockade or by 
assisting the Army to invade enemy territory, the enemy will require 
all his naval forces for defensive purposes in his home waters and 
will not be able to detach vessels to attack our ports. Thus, in the 
Busso-Japanese AVar the Japanese carried out strong offensive opera¬ 
tions against Port Arthur and consequently the Russian naval forces 
there were unable to attempt any offensive operations in Japanese 
pvaters. On the other hand, the Japanese did not attempt any opera¬ 
tions against Vladivostok and the Russian naval forces there were 
; able to make several raids into Japanese waters. 

If our forces will not be sufficiently strong to operate in enemy 
waters or if bases are not available, and we are therefore forced to 
remain on the defensive, the best plan would be for the fleet to take 
a position in a base well advanced from our coast line. The enemy 
is thereby given the choice of passing our fleet in its advanced posi¬ 
tion or of attacking the advanced position itself. 

11313°—20 - 3 


17 




18 JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 

There are the following disadvantages for an enemy force passing 
our advanced base: 

1. It will have to proceed from its most advanced base direct 

to our coast without the use of an anchorage for refueling. 
Thus it must—if the two opposing nations are at a dis¬ 
tance from one another—either arrive off our coast with 
but a small amount of fuel in its bunkers or must refuel 
at sea. Both of these courses are almost impracticable. 

2. It will be subject to attack by the various forces of our fleet 

at the advanced base, particularly destroyers and sub¬ 
marines, during the period beginning at the time it passes 
our advanced base on its advance, and ending at the time 
it passes it on the return. This is a very serious dis¬ 
advantage. 

3. If we desire to force a general action upon the enemy, either 

immediately or after the enemy forces have been reduced 
by destroyer or submarine attacks, his retreat to his home 
bases is cut by our forces, thus rendering a defeat par¬ 
ticular^ disastrous to him. 

4. As the enemy will not be able to maintain his lines of trans¬ 

portation with his home bases, due to the fact that our 
advanced base will be near his lines, he must either take 
with him a very large train or must carry through his 
operation very quickly. Either course imposes serious 
limitations on him. 

It therefore seems extremely improbable that the enemy would 
pass our advanced base. He must attack it. Therefore our defense 
is limited to one small position rather than an entire co^t line 
and our problem is greatly simplified. 

If we have no advanced base which may be occupied by the fleet 
upon the outbreak of hostilities or if our fleet is unable to occupy the 
advanced base in time it must select a base on our coast and operate 
from it. All advanced bases which might be seized and used by 
the enemy should be secured by local defenses. 

Of the various types of enemy vessels which may be used for 
attacks on the seacoast only submarines and very fast surface craft, 
such as battle cruisers, light cruisers, mine layers, destroyers, and 
aircraft carriers, can operate effectively unless the command of the 
sea along the coast is first gained by the enemy fleet; these types of 
vessels can not be used with their maximum effect unless their fleet 
has gained the command of the sea, for the fast surface craft may 
come in contact with superior forces of our fast surface craft, while 
their submarines will be attacked by our antisubmarine organization, 
which consists mainly of small vessels which would be unable to 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 19 

operate if the enemy enjoyed the command of the sea. Therefore in 
most cases the enemy will be required to support his attacking ves¬ 
sels by superior squadrons of battleships. 

The enemy would be very loath to use his battleships in this way, 
because they would be exposed to the attack of our submarines and 
destroyers. In the World War the British were willing to risk any 
ships but modern battleships in operations against German bases. 
The presence of the German high sea fleet would have compelled 
the British to have used their battle fleet as a support for any British 
vessels detailed to attack Heliogland. As the British could not risk 
their modern battleships in such dangerous waters, Heligoland was 
never attacked. On the other hand, the German high sea fleet could 
not protect their bases in Belgium, and therefore the British were 
able to attack them without bringing their battle fleet into danger¬ 
ous waters, although it was so stationed that it could have cut off the 
retreat of the high sea fleet had it attempted to interfere with the 
operations of the British destroyers and cruisers used in blocking 
Zeebrugge and Ostend and the monitors used in the frequent bom¬ 
bardments. 

There are, however, many cases where our fleet will not be able to 
afford this protection to the coast. This applies especially to our 
outlying possessions which are much nearer the home bases of an 
enemy than they are to our home bases. Again, our fleet may be so 
inferior in fighting strength that a general action must be avoided, 
and it must therefore be based on a strongly defended port. It will 
always be desirable for our fleet to keep in port a large part of the 
time in order to conserve fuel, to repair machinery, and to be secure 
from the attacks of enemy submarines and destroyers. This makes 
it necessary for us to have ports so protected that our fleet will not 
be exposed to the attacks of these craft. The British battle fleet was 
compelled to remain at sea for nearly all the time during the first 
months of the war because it had no base protected against German 
submarines. This cruising, which served no offensive purpose, 
caused many bad machinery breakdowns. 

For these reasons, the naval coast defense forces, the Army har¬ 
bor defenses, and the mobile forces of the Army are also necessary 
for coast defense. 

AIRCRAFT ATTACKS ON SEAPORTS. 

1. Enemy aircraft attacks on our seaports can be launched in two 
ways: 

(a) From a land base. 

(&) From a ship base. 

In order to carry out an effective bombing attack it is necessary 
for the enemy to have a base within several hundred miles of the 


20 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 


object of attack. There are at present practically no places in the 
possession of a possible enemy from which enemy air raids may be 
launched over the ocean at our seaports. 

There are very few places on either coast which might be seized 
by an enemy during the war and used as aircraft bases for attacks 
on our ports. 

Aircraft attack from land bases, therefore, does not require special 
attention. The measures for preventing such air attacks will be 
similar to those which will be described for preventing air attacks 
launched from ships, except that instead of counterattacking the 
ships used as bases the land bases should be counterattacked either 
by planes and ships or by Army forces. 

In launching attacks from a ship base two kinds of ships can be 
used: 

(a) Aircraft carriers, which carry planes assembled and ready 
for use on short notice, and have a flying-off deck from 
which airplanes may rise and upon which they may land. 
(h) Aircraft tenders, which may either accompany seaplanes 
as they fly from place to place, providing quarters for 
the plane crews, supplies of fuel, oil, and spare parts 
and repair facilities, or which may carry the seaplanes 
or airplanes, so that after arriving at the place for 
launching the attack seaplanes may be assembled and 
lowered over the side and airplanes .taken ashore and 
assembled for use from a beach or field. 

The development of aircraft carriers has been rapid and generally 
successful. Fighting planes, observation planes, scouting planes, 
and torpedo and bombing planes may be used. The planes are stowed 
below; the smaller types can be raised to the flying-off deck by ele¬ 
vators and can take off immediately; the larger types must have their 
wings attached after having been raised to the flying-off deck and 
this causes a certain delay in sending them out and receiving them 
aboard. Specially designed aircraft carriers of 10,000 tons can 
carry about 25 planes of various types. Landing on the flying-off 
deck presents some difficulties, and a considerable percentage of 
crashes must be expected, especially in rough weather. 

The use of a stabilizer to decrease the rolling of a carrier while 
planes are landing should greatly improve landing conditions and 
reduce the number of accidents. 

In carrying out a bombing attack from a carrier, the bombing 
planes should be accompanied by fighting planes for protecting them 
from the attack of enemy fighting planes, if any are present, and for 
assisting the bombers by attacking with machine-gun fire and small 
bombs enemy forces on the ground, particularly antiaircraft batteries 
and fire-control stations. 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 


21 


Aircraft tenders may be used in four ways by an enemy: 

1. To carry reserve fuel, bombs, and torpedoes, and to make 

necessary repairs for large seaplanes, which actually fly 
from the enemy bases to the place from which the attack 
on our port is to be launched. 

2. To assemble seaplanes and lower them into the open sea for 

taking off. 

3. To assemble seaplanes and lower them into calm water in 

the lee of the land for taking off. 

4. To place on shore airplanes which may be then assembled 

so as to take off from a suitable beach or field. 

When the planes assigned to attack a certain port have to fly from 
their shore bases to the place from which the actual attack is to be 
launched there will usually be little chance of success, unless the 
enemy has air bases reasonably close to the ports to be attacked, or 
unless there are sheltered anchorages spaced at intervals of less 
than 500 miles along their line of advance, in which they can re¬ 
ceive supplies from their tenders and have repairs made. 

As a general rule, it will be an unsatisfactory operation to attempt 
to use seaplanes which have to take off from the open sea. Only in 
weather much better than the average will large seaplanes with a 
heavy load of bombs be able to take off in the open sea. However, in 
many cases an enemy will be forced to resort to this method of attack, 
because all the sheltered anchorages will be under the gunfire either 
of fixed or mobile batteries. This condition prevails on our Pa¬ 
cific and Atlantic coasts. When planes are to be launched in the open 
sea accurate weather predictions will be invaluable. 

£ Wherever possible, an enemy wishing to use seaplanes in a bombing 
attack -will attempt to find sheltered water from which his planes 
may take off. If he is making a surprise attack he will select a loca¬ 
tion in which there are either no inhabitants to report his presence 
to our forces or no means of communication for making such reports. 

. There are many such places near the Pacific entrance to the Panama 
| Canal which an enemy could use for a surprise attack. There are 
some places in the Hawaiian Islands from which an enemy might 
launch a surprise air attack upon Pearl Harbor, and there are many 
places not covered by gunfire which could be used if surprise were 
not considered necessary. 

Airplanes are more efficient than seaplanes for bombing and torpedo 
attacks because they can carry a greater load of bombs or a larger 
torpedo. It is possible that aircraft tenders could land bombing and 
torpedo planes near the port to be attacked, assembling the planes 
ashore and having them take off from a beach or field. There are 
probably places near the Pacific entrance to the canal where this 
could be done without reports reaching our forces. While it would 
hardly be posible for an enemy to effect a landing on Oahu, he could 


22 JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 

land on another island in the Hawaiian group and launch air attacks 
from there against Pearl Harbor. 

The objects of attack by enemy aircraft will usually be: 

A. By bombs— 

1. Dry docks. 

2. Navy-yard shops and fuel-oil tanks. 

3. Naval vessels. 

4. Merchant vessels. 

5. Industrial plants of military importance. 

B. By torpedoes— 

1. Caissons of dry docks. 

2. Floating dry docks. 

3. Naval vessels. 

4. Merchant vessels. 

Now consider the ways in which enemy air attacks launched from 
aircraft carriers or tenders may be countered. The most effective 
method is to scout for and attack the enemy aircraft carriers and 
tenders. 

The following naval forces may possibly be available for scouting 
for enemy aircraft carriers and tenders: 

1. Submarines. 

2. Aircraft. 

3. Patrol vessels. 

4. Destroyers. 

5. Cruisers. 

Submarines will be very efficient for such scouting operations. The 
latest boats have radio with a sending radius of about 300 miles and 
could quickly report all enemy vessels sighted. Submarines have the 
additional advantage that they will be in a position to make an im¬ 
mediate attack on the aircraft carrier and will not themselves be ex¬ 
posed to attack unless the enemy’s planes which can rise from the 
flying-off deck are equipped with depth bombs. 

Aircraft will also be very efficient scouts. Both dirigibles and sea¬ 
planes can be used. Dirigibles have a much longer radius of action 
than seaplanes and can thus remain on their scouting stations for a 
longer time. They are, unfortunately, somewhat vulnerable to at¬ 
tack by enemy fighting planes which aircraft carriers could send up. 
Small nonrigid Blimps could not withstand the attack of fighting 
planes. Large rigid dirigibles would be more satisfactory; they could 
probably escape by means of their ability to climb faster and main¬ 
tain a greater altitude than heavier-than-air craft; even if overtaken 
they could make a moderately good defense if a noninflammable gas— 
such as helium—is used. 

The seaplanes available for scouting from shore bases are .scout¬ 
ing planes and patrol planes. Both types would be excellent for 



JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 23 

locating and reporting the enemy aircraft carriers and tenders; patrol 
planes, being moderately large, slow-speed seaplanes, would be vulner¬ 
able to attack by enemy fighting planes. On the other hand, the 
scouting planes, being medium-sized fast seaplanes with a heavy ma¬ 
chine-gun armament and being specially designed for fighting, would 
be able to maintain a position near the enemy ship, beating off attack¬ 
ing enemy planes. 

Destroyers and cruisers would be very well suited for locating and 
reporting enemy aircraft carriers or tenders, but being very valuable 
ships would seldom be available for this duty. 

The following vessels may possibly be used for attacking enemy 
aircraft carriers and tenders: 

1. Submarines. 

2. Aircraft. 

3. Minelayers. 

4. Destroyers. 

5. Cruisers. 

Submarines will be especially efficient for attacking enemy aircraft 
carriers, and, when the fleet is not present, they will be the principal 
instrument for breaking up this form of coast attack. 

Not under even the most favorable conditions will dirigibles be 
able to carry out bombing attacks on aircraft carriers or tenders. In 
clear weather naval airplanes and seaplanes carrying bombs and tor¬ 
pedoes and acting without the assistance of surface craft will have 
only a fair chance of making successful attacks, except when they are 
carried out simultaneously by large numbers of planes. In misty 
weather or when the clouds are low even a single plane has good 
chances of making a successful attack with bombs or torpedoes; dur¬ 
ing rain squalls, at dusk, or at night, when the sea can be lighted with 
parachute flares while the planes remain invisible, the chances of suc¬ 
cess are even better. One hit by a bomb on the flying-off deck of a 
carrier will probably prevent planes from leaving the deck or landing. 

Contact mines may be placed in the sheltered anchorages which 
aircraft carriers or tenders might use. This, however, is a very 
questionable operation and one which would be very expensive for 
the results which would probably be obtained. 

Destroyers and cruisers, attached to the fleet, may be within strik¬ 
ing distance of enemy aircraft, carriers, and tenders when reported; 
in such cases they could often be spared to carry out attacks on the 
enemy vessels. Cruisers will usually have superior gun power and 
may attack at any time; destroyers will usually make night attacks 
with torpedoes. 

The Naval Communication Service will be very valuable in all 
coastal operations as an instrument for directing the patrolling and 


24 JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 

scouting operations; for receiving reports from scouting and pa¬ 
trolling vessels announcing the location of enemy vessels; for broad¬ 
casting this information to other vessels at sea and for informing 
the Army sector and subsector commanders; for issuing instructions 
for vessels at sea to concentrate on and attack the aircraft carriers 
and tenders. The radio direction stations will be very useful for 
locating enemy vessels which use radio. 

In case the enemy escorts his aircraft carriers and tenders by 
other important vessels such as cruisers, battle cruisers, or battle¬ 
ships, a decision must be made as to whether the carriers themselves 
or the supporting vessels should be attacked. This decision depends 
on an estimate of the following: 

1. The damage which the enemy may inflict upon our shore 

facilities by his bombing or torpedo attack, and the in¬ 
fluence of this possible damage upon the entire cam¬ 
paign; in this estimate, we should consider the zVrmy 
forces available for keeping off the enemy’s bombing 
planes, such as antiaircraft guns and pursuit planes. 

2. The relative importance for us of -sinking or damaging 

the carriers or the supporting vessels; in this estimate, 
we should consider the relative strengths of our own and 
the enemy Navy in the types of ships subject to attack. 

3. The relative chances of sinking or damaging the carriers 

or the supporting vessels, including the chances for mak¬ 
ing contact and of carrying out successful attacks. 

For example, assume that an enemy aircraft carrier is attempting 
to penetrate to within a short distance from the Pacific entrance to 
the canal; that it is known to carry large bombing planes; that the 
Army defenses are probably insufficient to prevent bombing attacks 
on the locks and spillway; that it is known that the bombs carried by 
the enemy planes are likely to cause serious damage to the locks and 
spillway; that the canal is vitally necessary for our Naval Transport¬ 
ation Service; that the enemy carriers are escorted by several light 
cruisers. In this case, every effort should be made to attack and sink 
or damage the carriers before their planes are able to get off. 

As another example, assume that an enemy aircraft carrier, 
escorted by a battle cruiser, is attempting to gain a favorable posi¬ 
tion for launching a bombing attack on an unimportant naval sta¬ 
tion; that this station is well protected by antiaircraft guns and 
pursuit planes, and that, even if the enemy could make hits, our cam¬ 
paign will not be materially retarded; that we have no battle cruisers, 
and, therefore, the sinking of the enemy battle cruisers will be an 
important gain for us. In this case the greatest effort should certainly 
be concentrated on sinking or damaging the enemy battle cruiser. 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 25 

MINE-LAYING ATTACKS OFF THE SEACOAST. 

The mine has become a very effective offensive weapon. The 
Japanese used mines offensively at Port Arthur; all nations em¬ 
ployed them with great effect during the recent war for blocking 
entrances to ports and even to whole sea areas. The Dover barrage 
was finally so perfected in 1918 that German submarines were unable 
to pass through. The North Sea barrage had become very effective 
by the time the armistice w T as signed. Had the war continued longer 
the German submarines would soon have found both exits from 
the North Sea closed to them. Mines will undoubtedly be laid ex¬ 
tensively in the next war near the entrance to enemy ports, both with 
the object of completely closing the entrance to the port and of in¬ 
flicting losses upon enemy naval vessels entering or leaving port. 

Mines may be laid offensively by the following types of vessels: 

(1) Minelayers, carrying about 350 mines. 

(2) Light minelayers, carrying about 60 mines. 

(3) Submarine minelayers, carrying from 25 to 50 mines. 

There are, in general, the following types of anchored mines: 

(1) Contact mines. 

(2) Controlled mines. 

Contact mines explode when a vessel comes in contact with the 
mine itself or with a wire antenna spread from the mine in a vertical 
direction. This antenna may be stretched upward by means of a 
float or may stretch downward along the mooring cable, or both. 
Mines can be laid effectively in 1,000 feet of water, and experiments 
are under way for mining in greater depths. The length of antenna 
can be varied to fit the conditions to be met. Thus, if it were desired 
to mine surface vessels, the charge should be exploded practically 
against the hull, and a very short antenna could be used above the mine 
or the antenna could be eliminated altogether. At the same time, 
if it were considered that the mine charge would be effective against 
a submarine some distance below it (possibly 70 to 80 feet), a bottom 
antenna of this length could be used. One row of mines under the 
best possible condition with top and bottom antennae of 80 feet would 
cover a depth of 160 feet. Another row of mines could be laid below 
the first row to cover greater depths. The distance at which a mine 
explosion is effective against a submarine increases materially with 
the distance the mine and submarine are below the surface. 

' Controlled mines may be either anchored or ground mines. This 
is the general type of mine used by the. Army in coast defense, and 
is a very valuable type around harbor entrances and channels to be 
used by our own vessels. A controlled mine can be fired in any one 
of three ways. In the first method, the vessel’s position is plotted 
from shore observation stations, and at the proper time the mine is 
11313°—20-4 



26 JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 

fired by closing a circuit on shore. Second, a vessel striking a mine 
will cause a signal to be made at the switchboard on shore. The key 
is immediately closed and the mine fires. Third, power may be so 
turned on that when the mine is struck by a passing vessel it imme¬ 
diately fires. Controlled mines have a further advantage in that 
several mines can be fired simultaneously, thus making it probable 
that one or more explosions will be moderately close to enemy ves¬ 
sels. The mines have one disadvantage; this is that friendly vessels 
striking the mines will possibly damage and sink them. The enemy 
can not use controlled mines in our waters. He is limited to mines 
which explode automatically. 

Now consider the conditions most favorable for the laying of 
mines. It is important that the vessels doing the mining have open 
and unrestricted approaches to the ports in front of which mines 
are to be planted. The width of the actual harbor entrance itself is 
not a matter of much importance, for while a narrow entrance 
would be easier to close with mines, the mine-laying vessel would 
hardly dare to penetrate into such a narrow and dangerous area. 
If submarines are to be used for the mine laying, the water through 
which they must pass should be at least 50 feet deep, so as to allow 
them sufficient room for maneuvering. 

The currents, rise and fall of tide, and depth of water should all 
be a minimum. 

Currents cause a typical anchored mine to dip a number of feet 
below its set depth, as shown by the following table : 


Current, 
in knots. 

Length of 
mooring, 
in feet. 

Dip, 
in feet. 

1 

60 

0.3 

2 

60 

1.5 

3 

60 

8 

1 

180 

1 

■2 

180 

13 

3 

180 

43 

1 

300 

4 

2 

300 

45 


There are two kinds of currents to be considered: 

1. A steady current, usually along a coast. 

2. A tidal current, the direction of which changes about every 

six hours. 

A steady current whose speed is generally constant will not mate- 
■ rially reduce the effectiveness of mines. Such currents are usually 
of moderately low speed. The dips for the lowest and highest cur¬ 
rents which may be normally expected in a certain location should 
be averaged; the anchor cable to be let out should be lengthened by 
an additional number of feet equal to the average dip, provided this 






JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 27 

does not bring the mine to the surface when the current is at a 
minimum. This would be undesirable unless it is not important to 
conceal the location of the mine fields. 

A tidal current, on the other hand, decreases very materially the 
effectiveness of mines. The antennae of the mines provide a means of 
compensating to a slight extent for this loss of efficiency. If 10 feet 
of antenna is let out, and the mine is planted so as to be 15 feet be¬ 
neath the surface at slack water, the end of the antenna will be 5 
feet below the surface. Then when a current produces a dip of 15 
feet the mine itself will go to 30 feet beneath the surface and the top 
of the antenna to 20 feet, making the mine still effective against ves¬ 
sels of more than 20 feet draft. If the dip were 25 feet, two courses 
could be taken: 

1. Ten feet of antenna could be used, and the top of it would 

be 30 feet under water when the maximum dip of 15 feet 
was reached. 

2. Twenty feet of antenna could be let out, so that at maxi¬ 

mum dip the top of it would be only 20 feet under water. 
This would expose the antenna at slack water and Avhile 
the current was weak. In some cases it would be very un - 
desirable to expose the position of the mine field; in 
others this exposure would not be important. 

A dip of more than 15 feet, therefore, very materially decreases 
the efficiency of the mine; thus, with a length of mooring of 60 feet 
the mine will be effective in any current; with a length of mooring 
of 180 feet a current of 2 knots is allowable; with a mooring of 300 
feet a current of 1^ knots is allowable. For currents in excess of 
this a part of the explosive charge can be taken from the mine, in¬ 
creasing its buoyancy and decreasing the dip. 

A rise and fall of 15 feet has an effect similar to a tidal current, the 
maximum strength of which cause a dip of 15 feet. A rise and fall 
of this amount is therefore allowable. 

Mines are less effective in tropiral waters than in northern waters 
because they can be seen by aircraft down to 30 feet, the maximum 
depth to which they would be effective against surface vessels. 

The following naval craft can be used to operate against enemy 
mine layers and to clear the approaches to ports of mines which have 
already been laid: 

1. Submarines. 

2. Aircraft. 

3. Mine layers. 

4. Mine sweepers. 

5. Patrol vessels. 

6. Destroyers. 

7. Cruisers. 


28 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 


Submarines will be able to operate against all classes of enemy 
mine-laying craft. They will usually prevent mine laying by slow 
cruisers; against other types of mine layers they would not be so 
effective. Mines would probably be laid at night; therefore, enemy 
submarines would be difficult to locate, while enemy destroyers and 
fast mine layers would be difficult to hit with torpedoes on account 
of their high speed. Still, submarines, even if these are unable to 
score torpedo hits, will have an important moral effect and will force 
the enemy to hurry his operations. On the other hand, the sub¬ 
marines themselves may be damaged or sunk by the enemy mines. 

Aircraft will be effective for detecting and attacking enemy sur¬ 
face craft laying mines in daylight; they will also be effective in 
preventing enemy submarines from laying mines close inshore dur¬ 
ing daylight in tropical waters and will be moderately effective in 
all waters against submarine mine layers; they will, however, be of 
little use in the night against any type of mine layer. In tropical 
waters they can be used to locate mines after they are planted. 

The laying of contact mines as a defense against enemy mine 
layers is a questionable operation. These mines in most cases would 
be effective against our own ships and would greatly limit our freedom 
of action. We might, however, lay deep mine fields against enemy 
submarine mine layers which our surface craft could pass over 
without danger. Our submarines, however, would have to give these 
areas a wide berth except when on the surface. Other small mine 
fields could be laid in carefully selected locations, especially if we had 
reason to believe enemy mine layers would operate in known areas. 
In general, however, it must be realized that the laying of mines in 
our waters is a dangerous procedure because our vessels may enter the 
mine field through carelessness or some mistake or neglect in dissemi¬ 
nating information. Mines may also break adrift and become dan¬ 
gerous to our vessels. Wide entrances to important harbors should 
be closed with an antisubmarine.net, having a gate which can be 
opened for our vessels to pass through. 

Mine sweepers should be used to*sweep lanes in the approaches to 
ports and along the coast and to clear enemy mine fields reported. 
All shipping should be warned to avoid such mine fields until they 
have been cleared. 

Patrol vessels will be very useful to locate and report enemy vessels 
laying mines. Their listening devices, which are now effective to 
distances of about 10 miles, will make them especially valuable. Sub¬ 
marines when located can be attacked with depth charges. 

Destroyers may be used to search for and attack all enemy mine 
layers; submarines may be attacked by gunfire or depth charges; 
light mine layers by gunfire and possibly torpedo fire. Mine layers 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 29 

must usually be attacked by night torpedo fire, but this will probably 
not be effective if the enemy vessels have high speed. 

Cruisers will seldom be available for searching for enemy mine 
layers, but may be used to attack light mine layers or mine layers 
when they are reported by other vessels. 

TORPEDO, BOMBING, AND GUNFIRE ATTACKS ON VESSELS OFF 
THE SEACOAST. 

Attacks on vessels off the seacoast may be made by the following 
types of enemy naval vessels: 

Submarines. 

Aircraft carriers. 

Destroyers. 

Light cruisers. 

Battle cruisers. 

These vessels may be supported by battle squadrons. 

In general, these attacks may be met in three ways: 

1. By searching for the enemy craft to seaward of the coastal 

shipping routes,'and concentrating against them superior 
forces, at the same time withdrawing our merchant ship¬ 
ping temporarily from the area into which the raid or 
sweep is being made. 

2. By patrolling the area through which the shipping actually 

passes, attacking enemy vessels encountered. 

3. By forming the merchant shipping into convoys and es¬ 

corting them with naval vessels, for the purpose of coun¬ 
ter attacking all enemy vessels which attack the convoy. 

For defense against submarines, the third method has proved best, 
the escort consisting of destroyers, nonrigids, planes based on shore 
stations, and patrol craft. The second method may also be used, 
the same types of craft being employed. The measures already de¬ 
scribed for use against submarine mine layers will also be effective 
against submarines attacking with torpedoes. 

Against aircraft carriers the first method will probably be desir¬ 
able, except that our merchant shipping probably will not need be 
withdrawn if the enemy attack can be met in time. Our measures 
would be similar to those described for preventing aircraft attacks 
on shore stations. 

Against enemy destroyer raids the third method will be most 
desirable, but the others may be used in addition. 

Against frequent light cruiser raids the third method will be the 
best with cruiser escort for the convoys. If only isolated raids are 
made, the first method may be used. 

Against battle cruisers or battle squadrons the first method is the 
most desirable, our battle squadrons being held in readiness to meet 


30 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 


the enemy if his force is not greatly superior. If the enemy battle 
squadrons are greatly superior to all our forces available, our ship¬ 
ping must be withdrawn during their sweep, while our submarines, 
destroyers, and aircraft are concentrated upon them with the object 
of reducing the enemy’s superiority by torpedo attacks. 

TORPEDO FIRE INTO SEAPORTS. 

An open and unrestricted approach and a wide, straight entrance 
to the harbor are necessary for this form of attack; an open road¬ 
stead is the most favorable condition. If the attack is to be made by 
submarines there should be at least 50 feet of water right up to the 
entrance. Torpedo attacks during daylight, while possible for sub¬ 
marines, will probably be ineffective if proper measures are taken 
to counter them; during darkness attacks by destroyers and sub¬ 
marines running on the surface are possible. 

All the counter measures developed for use against minelayers will 
be effective against vessels making a torpedo attack on vessels in 
port. Submarines will be moderately effective; aircraft will make 
submarine attacks difficult during daylight, particularly in tropical 
waters. Small fields of contact mines may be laid in the approaches 
to the port in areas in which enemy vessels are expected to pass and 
in which our ships will not operate; in the case of an open roadstead, 
the entire anchorage may be inclosed by a mine field, preferably 
outside of torpedo range from the vessels at anchor. Patrol vessels 
with listening devices will be very useful to detect enemy vessels and 
to attack submerged submarines with depth charges. 

There are other methods which can be used in addition to those 
employed against minelayers. It will often be possible for the ships 
to anchor in positions where they will be out of the direct line of 
fire of torpedoes coming through the entrance. For example, vessels 
in Colon Harbor could take five courses to avoid torpedoes: 

1. Go alongside docks at Cristobal, where they would be out 

of the direct line of fire. 

2. Anchor to the southward of the docks, where they would be 

out of the line of fire. 

3. Anchor in the southern part of the harbor, where they 

would be distant 5,000 yards from the entrance and almost 
out of range. 

4. Anchor close to the breakwaters, where they would be 

practically out of the direct line of fire and could use 
their guns effectively against attacking craft. 

5. Go to Gatun Lake. 

Vessels could in some cases be moored bow and stem in the direc¬ 
tion of the entrance so as to present the minimum width of target 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 31 

for torpedoes. All vessels should screen lights at night and the 
entrance should not be indicated by navigational or other lights. 

A final method of defense is the torpedo net. These nets may be 
placed at the entrances to important ports which are exposed to 
torpedo attacks; they should have gates which can be opened for our 
vessels. Torpedoes, fitted with net cutters, can penetrate torpedo 
nets. As torpedo nets are a very costly method of defense, they 
should not be used if there are other effective means which can be 
used to counter torpedo attacks on vessels, in our seaports. 

BLOCKING ATTACKS ON SEAPORTS. 

The Merrimac was the first blockship in modern naval wars; her 
attempt to close the narrow entrance to Santiago Harbor was un¬ 
successful. The Japanese made repeated but ineffective attempts 
to block Port Arthur. The British succeeded in blocking for a time 
the entrance to the Zeebrugge Canal with two ships, but failed twice 
at Ostend. 

Only very narrow entrances, as at Pearl Harbor or Balboa, can 
be blocked; the operation can be carried out only under cover of 
darkness, and this of course adds to its difficulty and uncertainty. 
Blockships will usually be escorted by a naval force sufficient to pro¬ 
tect them against attacks of the naval vessels assigned to the local 
defense. The enemy may carry out diversions to distract the atten¬ 
tion of the defenders, such as— 

1. Bombing attacks by aircraft. 

2. Bombardment by surface vessels and submarines. 

3. Landing attacks. 

The blockships may be hidden from the shore batteries as long as 
possible by a smoke screen, laid by small craft. As it will be diffi¬ 
cult to find the entrance, rockets or flares may be used. In the 
second attack on Ostend a million candlepower calcium flare was 
lighted. Small craft may accompany the blockships to take off the 
crews after the ships are sunk. Enemy submarines, without escorts, 
might be used as blockships. 

Our submarines will probably not be able to break up the attack 
due to the strong escorting force; they should, however, be able to 
make torpedo attacks on the escorting vessels and to give warning of 
the approach of the enemy. Aircraft probably will be of little use on 
account of the darkness. Contact mines will be effective against 
blockships and large fields of them should be laid in the approaches 
to a harbor when blocking attacks are expected, straight* and Tride 
channels being left for our vessels. Patrol vessels with listening 
devices will be valuable for reporting the approach of the enemy. 
Nets and booms will not be of any use, as was proven at Zeebrugge. 


32 JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 

The most effective measure for countering this form of attack will 
be to search for and locate the attacking force while still at a distance 
from the port to be attacked and to concentrate a superior force 
against it. 

BOMBARDMENT OF SEAPORTS BY NAVAL VESSELS. 

There are, in general, two forms of bombardment of seaports: 

1. Bombardment by surface craft. 

2. Bombardment of submarines. 

As a general rule, bombardment of our ports by surface craft is 
possible only when the enemy has the command of the sea; it is true 
that on several occasions the German surface craft bombarded Eng¬ 
lish coast towns, but on no occasion was any important damage 
caused; the last time a raid was attempted the German battle cruiser 
division was brought to action and the Blucher was sunk. These 
raids, moreover, w y ere made mostly for political and moral effect. 

But while the command of the sea is usually necessary for bom¬ 
bardments by surface craft, submarines will be able to bombard ports 
when their own surface craft are held securely in port. Submarines, 
of course, will not attempt to attack large and important seaports 
wdiere elaborate defenses will be prepared. They are limited to raids 
on small ports, which are usually undefended, and to exposed naval 
stations, such as air stations and radio stations. 

The main defense against bombardment will usually be provided 
for by the Army; the Navy will attack the enemy vessels taking 
part in or supporting the bombardment in accordance with the pro¬ 
cedure already recommended for other forms of enemy attack. 

PENETRATION INTO A HARBOR OR WATER AREA BY NAVAL 

VESSELS. 

This operation has two general forms: 

1. The forcing of a passage by main force. 

2. The penetration of a passage by light craft by stealth. 

Penetration into a harbor is a very difficult operation and will 

seldom be attempted. The penetration of a narrow passage, such as 
a river or strait, offers better chances* of success. 

The forcing of a passage by main force was accomplished a num¬ 
ber of times in the Civil War by Farragut. In the World War it was 
attempted three times: 

The attempt of the British to force the Dardanelles. 

Two attempts of the Germans to force the entrance of the Gulf 
of Riga. 

Of these only the second attempt to seize the Gulf of Riga was suc¬ 
cessful, and this can be accounted for largely by the demoralization 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 33 

of the Russians. These operations show the difficulty of forcing 
even a passage a number of miles wide. The forcing of a harbor 
entrance will be much more difficult and will seldom be attempted. 

As one of the principal means of defense will usually be the laying 
of large fields of contact mines the first operation of the enemy 
will be to sweep a passage through the mine fields. The sweepers 
will be supported by destroyers and light cruisers. When a passage 
is cleared the heavy ships will arrive off the port, escorted by de¬ 
stroyers to protect them from submarine attack. These heavy ships 
will probably then carry out prolonged bombardments of the shore 
batteries. If the batteries are silenced, or their fire greatly reduced, 
the fleet may then attempt to run past them during the daylight, 
possibly using a smoke screen as an additional protection. If the 
batteries are still strong a dark night will probably be the best time 
to run the forts. Air attacks will probably be carried out all through 
the operations. 

All weapons will be effective in defeating an attempt to force the 
entrance to a seaport or a narrow strait, particularly large fields of 
contact mines, torpedo and bombing planes, and submarines. 

Often an entrance into a large harbor, a bay, or a sea will be so 
well defended by batteries that it will be impracticable for large 
vessels to force it. However, it may be possible for light craft, par¬ 
ticularly submarines and destroyers, to run past the defenses and 
operate inside. The best examples of this were the penetration of 
the Dardanelles by British submarines which operated in the Sea 
of Marmora and the penetration of the entrances to the Baltic by 
British submarines which worked effectively. against the German 
trade with Sweden. 

There are, in general, three methods of preventing this form of 
attack: 

1. By gunfire of forts at the entrance. 

2. By closing the entrance with mine fields and obstructions. 

3. By using a naval force to attack the enemy while passing 

through the entrances or after he has reached the harbor 
or body of water inside the entrance. 

In order to use the gunfire of shore batteries effectively, the enemy 
vessels attempting to pass the defenses should be discovered while 
still at some distance from the entrance and illuminated by star 
shells and searchlights. Small patrol vessels similar to our sub¬ 
marine chasers would be well suited for this purpose. They have a 
small searchlight, and the 3-inch antiaircraft gun could be used for 
throwing star shells over the enemy. If discovered in time the gun¬ 
fire of shore batteries should prohibit the entry of cruisers and pos- 


34 JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 

sibly destroyers. Submarines, however, offer such a small target, 
even when awash, that it is doubtful whether they could be kept from 
passing through an entrance a number of miles wide by the gunfire 
of shore batteries alone. 

Nets, booms, and mine fields should be effective in keeping out 
enemy submarines. Mines will be effective against destroyers and 
cruisers, but nets, and booms will probably be broken b} 7 them with¬ 
out serious injury to themselves. Their greatest chance of being 
injured is that their propellers maye be fouled. Small nets, which 
are held in position by light lines, would be useful for this purpose. 

In CRse it is not considered that these two methods are sufficient, 
local naval forces must be used. Submarines will not be very effec¬ 
tive in preventing the entrance at night of the enemy vessels, par¬ 
ticularly submarines and destroyers, but they will be very useful in 
attacking all classes of enemy vessels after they have entered, as in 
this case they will be able to operate in the daytime.. Destroyers and 
cruisers will be necessary for attacking with gunfire and depth 
charges enemy vessels attempting to enter and will be needed for 
maintaining the command of the water area inside against enemy 
vessels which pass the entrance. 

LANDING ATTACKS. 

Landing attacks may assume either of two general forms: 

1. Raids by small forces for the temporary occupation of 

positions on shore for effecting military damage. 

2. Attacks in force. 

Examples of raids in the World War were the seizure of the forts 
on the southern shore of the Dardanelles for the purpose of destroy¬ 
ing them after their garrisons had been driven off by the bombard¬ 
ment of naval vessels, and the British landing on the mole of Zee- 
brugge during the blocking attack for the purpose of destroying 
the German seaplane base and shore batteries on the mole and to 
create a diversion for the blockships. Such raids may be carried 
out by landing forces formed from the crews of naval vessels or by 
small detachments of troops carried on naval vessels or transports. 

Landing attacks in force are illustrated by the operations of the 
British Army at the Dardanelles and the “ Great Landing ” which 
the British were prepared to make on the Belgian coast. 

In general, the following operations may be carried out by naval 
forces to break up a landing attack: 

1. Operations for gaining information of the approach of 

the enemy and of the locality in which he intends to land. 

2. Attacks on enemy naval vessels and transports. 

3. Attacks on enemy troops while landing. 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 


35 


It may be assumed that when landings in force are made the 
transports will be accompanied by naval forces superior to our naval 
forces available for defense. This condition justifies the use of alL 
our available naval forces against the attacking enemy force. 

It is very important to locate the approaching enemy forces while 
still at a great distance from the coast, so that naval and military 
forces may be concentrated against them. Aircraft (particularly 
rigid dirigibles), destroyers, and cruisers will be effective for obtain¬ 
ing this information by searching out an area extending out several 
hundred miles from the coast and reporting all enemy vessels or 
forces sighted. When the enemy transports are definitely located, 
the searching operations should be discontinued, unless other enemy 
transports are expected; the vessels used in the searching operations 
should be used for contact scouting, relocating the transports at short 
intervals, or, if possible, keeping in constant touch with them, so that 
their position will be known at all times. 

For making attacks on the transports and naval vessels escorting 
them submarines, destroyers, and aircraft will be very effective. 
Bombing and torpedo planes will be particularly valuable. Assum¬ 
ing that our battle squadrons are so inferior as not to be able, to risk 
a general action, they should, nevertheless, be held in readiness and 
kept at sea in close proximity to the enemy forces in order to take 
advantage of any particularly favorable opportunity for attack. 

In the case of attacks on insular possessions submarines will be 
particularly valuable as a defensive force as they are not dependent 
upon the support or assistance of other vessels and have a secure 
means of retreat should the possessions be captured by the enemy. 

Contact mines may be used, but it must be realized that contact- 
mine fields constitute a menace to our own forces as well as those of 
the enemy; they also limit our activities; thus it is a principle that 
mine fields should never be laid for the purpose of repulsing a land¬ 
ing attack until the attacking force is sighted or there is good reason 
to believe that an attack is imminent. This principle limits the use 
of mines to the following: 

(a) To close narrow approaches to landing places, such as 

small unfortified harbors. 

( b ) To form fields off the coast across the line on which the 

attacking force is approaching. 

( c) To form fields off narrow beaches or landing places, so 

as to deny them to the enemy, allowing the naval and 
military forces to concentrate for the defense of other 
sectors. 

Attacks on the enemy troops while they are landing in small boats 
may be carried out by bombing and fighting planes. 


36 JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 

PROJECTS FOR SEACOAST DEFENSE BY THE ARMY AND NAVY. 

The necessary military and naval defenses for any particular sec¬ 
tor of the coast or insular possession, should be determined by the 
foregoing general principles. The following decisions must be 
made: 

1. With what power or combination of powers is there a rea¬ 

sonable possibility of war. 

2. What degree of protection will the fleet probably afford 

against the attacks of these powers by its operations 
against enemy naval forces. 

3. Which of the above eight forms of attack can the enemy 

make with reasonable chances of success. 

4. Plow can each form of enemy attack be best countered by 

the Army and Navy. 

5. What combination of military and naval defenses will suc¬ 

cessfully repulse all forms, or combinations of forms, of 
attacks. 

When these decisions are made, the following estimates should be 
set down: 

1. How soon after the beginning of the war may the various 

forms of enemy attack be expected. 

2. How soon after the beginning of the war may the military 

equipment and personnel and naval vessels, equipment 
and personnel necessary for defense be provided in the 
United States. 

3. What time will be required for this equipment and these 

vessels to reach the seacoast exposed to attack, consider¬ 
ing the fact that the enemy may take measures to prevent 
this equipment and these vessels from reaching the area 
to which they are assigned. 

Then the final decisions must be made: 

1. What part of the necessary military equipment and per¬ 

sonnel must be permanently installed on the coast ready 
for instant operation. 

2. What part of this equipment may be stored on the coast 

ready for immediate installation after the declaration of 
war. 

3. What part may be stored in other places and transported to 

and installed on the coast after the beginning of war. 

4. What part may be manufactured or provided after the 

declaration of war, and shipped to the coast for installa¬ 
tion. 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 37 

5. What naval vessels of the district forces must be per¬ 

manently stationed during peace near the seacoast to be 
defended. 

6. What equipment, such as dry docks, repair facilities, mines, 

spare torpedoes, fuel, nets, etc. must be maintained on the 
seacoast to be defended. 

7. What naval vessels of the district forces should be sent to the 

seacoast exposed to attack after the declaration of war. 

8. What naval equipment should be sent to the seacoast ex¬ 

posed to attack after the declaration of war. 

These decisions constitute a logical Army and Navy project for the 
defense of a sector of the seacoast. 


Part III. 


A POSITIVE SYSTEM OF COAST DEFENSE (ARMY). 


1. The present war has so materially modified our ideas as to 
land and coast defense by the introduction and development of new 
means and methods of combat on the sea, on land, and in the air 
that it has become necessary for the Army to undertake a revision 
of practically all of its defense projects and plans. 

2. Existing plans have, in general, been based upon the idea of 
defending important seaports, naval bases, etc., by the occupation 
of selected covering positions. With our present increased resources 
in materiel, personnel, and war experience, a more aggressive atti¬ 
tude of defense is warranted. ^Tt is proposed to show in this memo¬ 
randum that by a properly organized system of beach defense of the 
favorable landing places near all vitally important objectives it will 
be possible positively to secure the United States against invasion 
from the sea, even should we lose command of the sea in both oceans. 

3. The scheme herein outlined is based upon the idea that a suc¬ 
cessful invasion of the United States must be directed against cer¬ 
tain vital areas, and that the problem of defense against invasion 
from the sea is solved if large landing operations are prevented in 
those seacoast sectors which cover these vital areas. 

4. These vital areas include the following: 

(a) The portion of the United States covered by the seacoast 

line from Portland,'Me.., inclusive, to Chesapeake Bay, 

inclusive. 

(b) The southern California area from San Diego, inclusive, 

to Los Angeles, inclusive. 

( c ) The San Francisco basin. 

( d ) The area including Puget Sound and the mouth of the 

Columbia. 

Certain other areas contiguous to the South Atlantic and Gulf 
coasts may properly be added to the above. But in any event it is 
obvious that the portions of the coast line of critical strategic impor¬ 
tance are of limited extent compared with the total extent of the 
coast line. 

38 



JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 39 

5. But within any particular seacoast sector a reconnaissance of 
coast line will show that only a limited portion of the coast is favor¬ 
able for landing operations, and that among beaches favorable for 
landing operations only a limited number are favorably located 
with reference to important military objectives. A positive system 
of coast defense thus resolves itself into the defense not of the entire 
coast line, but of a limited number of favorable landing places all 
included within a limited number of critical strategical areas. The 
basic idea is this: That the enemy must be denied access to any 
landing place upon which he could quickly establish himself in force, 
but it is not necessary to defend places where a landing would be 
so difficult that an enemy would be unable to land in sufficient 
strength before our reserves could be brought up in numbers adequate 
to dislodge him. 

6. In order to illustrate this conception of a system of positive coast 
defense*, a hypothetical seacoast sector is shown on the attached map. 
Near the center of this sector is the important harbor A, a large sea¬ 
port B, a'navy yard C, and two seacoast fortifications, d and d' com¬ 
manding the entrance to the harbor A. Back of the seaport is a popu¬ 
lous basin more or less surrounded by mountains. E and F are trunk¬ 
line railways leading to the interior of the continent. G, H, and I 
are important railways leading to adjoining coastal areas and there 
connecting with other trunk lines to the interior. The basin is pro¬ 
vided with connecting railways. There is also an extensive system of 
tramways and highways along and throughout the basin which are 
not shown on the map. The harbor A and the city B, with the ad¬ 
joining basin, would be an important objective for an enemy having 
command of the sea. 

7. A reconnaissance of the coast line reveals the following charac¬ 
teristics : 

1- 2. This beach is favorable for landing operations, but is 

130 miles from B. The enemy would have to advance 
through difficult passes through the mountains at K. 

2- 3. A difficult and precipitous coast. 

3- 5. A favorable beach adjacent to the small unfortified har¬ 

bor 4. An enemy landing here might establish a sub¬ 
base at 4. 

5- 6. A difficult beach, with few good landing places and no 

good communications. 

6- 7. A beach exceptionally favorable for landing opera¬ 

tions ; 7 is about 20 miles from the seaport. A strong 
mobile force, if unopposed, might land here and se¬ 
cure a footing in rear of the harbor defenses. 

7- 8. A difficult beach covered by reefs. 


40 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 





JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 41 

8-9. A favorable beach for landing but not favorable for a 
speedy advance on account of the shallow tidewater 
at L. 

9-10. A difficult beach, covered by reefs, impracticable for 
landings on a large scale. 

11- 12. A favorable beach for landing operations partly cov¬ 

ered by fire from the seacoast fortifications at d'. But 
in favorable weather an enemy landing here might 
attack the fortifications from the land side as a first 
step toward securing the harbor. 

12- 13. A difficult beach covered in places by reefs and gener¬ 

ally impracticable for landing operations on a large 
scale. 

13- 14. A favorable beach, from which the minor harbor 15 

might be secured as a sub-base. 

15- 16. A more or less impracticable beach. Few good landing 

places and few communications through the moun¬ 
tains. 

16- 17. A beach favorable for landings, but a long distance 

from the objective. Difficult communications through 
the mountains at M. 

8. Before considering the positive defense of the indicated sector, 
the land-defense plans existing prior to the war may be considered. 

Permanent fortifications .—These are shown at d and d'. They 
are modern seacoast fortifications designed to resist a direct naval 
attack and to prevent a long-range bombardment of the seaport B 
and the naval base C. It is considered that the armament is still 
adequate for the assigned missions. Two additional long-range, 
high-powered guns were authorized by the Board of Review just 
before the war, but it is possible that these may not be installed, as 
certain types of railroad artillery procured during the war are being 
considered as suitable equivalents. 

Mobile forces .—The field forces available before the war were very 
limited in number and consisted of a few Regular and National 
Guard regiments without divisional organization. Plans for organ¬ 
izing new troops were unsettled, few suitable reserve officers were 
available, and only limited equipment and munitions were procurable. 

Land-defense plans .—With the limited field forces available there 
was practically no basis for complete defense plans. Detailed plans 
for the immediate defense of the fortifications against naval raids 
had been drawn up and approved. A defensive line covering the 
fortifications and the city had been established, but the provision of 
a suitable garrison, armament, and equipment was highly conjectural. 


42 JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 

9. In considering the revision of the land-defense projects after 
the war it becomes apparent that there is a great change in the sit¬ 
uation as regards available resources: 

(a) The principle of the selective draft adopted at the outbreak of 

the war may be assumed as the future national policy in the 
event of a great war. This assures a definite basis for the de¬ 
velopment of man power, 

(b) The war has developed a large body of more or less experienced 

officers. Under a sound policy of national military education 
this body of officers should be perpetuated. 

( c ) Large quantities of armament, munitions, and equipment pro¬ 

vided for the war Army are still available and the capacity 
of our industries to augment these supplies has been greatly 
developed. 

(d) A large number of our officers have acquired important expe¬ 

rience in command and staff duties during the war. 

( e ) Our General Staff has acquired experience in the practical 

handling of large bodies of troops and this experience is to be 
perpetuated and transmitted through our military educational 
system. 

(/) Many tactical methods, weapons, and mechanical appliances 
recently developed in the land warfare are especially appli¬ 
cable to the problems of coast defense. 

10. Having in view the advantages enunciated in the preceding 
paragraphs we may consider the best methods now permissible for 
the complete defense of the coast sector shown in the sketch map. 

Assuming that the seacoast fortifications are capable of defeating 
a direct naval attack on the harbor, and that an efficient observation 
service is maintained along the entire coast line of the sector, it is 
obvious that the enemy can secure a footing only by landing opera¬ 
tions at one of the favorable beaches, 3-5, 6-7, 11-12, and 13-14. 

If, then, it is practicable to defeat serious landing operations on 
these beaches, the tactical measures accomplishing this result con¬ 
stitute a complete and positive defense of the entire sector. 

11. It is believed that a properly constituted mobile detachment 
of reasonable strength can accomplish this object by preventing 
landings at 4-5, 6-7, 11-12, and 13-14. Beaches 1-2 and 16-17 and 
similar beaches more remote from B need not be considered in deter¬ 
mining the strength of the necessary mobile garrison of the sector. 
They are so remote from the objective and separated from it by such 
difficult country that their use, if attempted, can be met by re¬ 
enforcements from the general strategic reserve. This is an illustra¬ 
tion of the principle that landing operations on a sufficient scale to 
form the basis of invasion must be within striking distance of a 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 43 

harbor where an enemy can secure or extemporize facilities for un¬ 
loading artillery and other heavy material of war. 

12. Whether a positive defense against landings is feasible for 
any extensive sector or for the United States as a whole must 
depend upon its relation to the general problem of economy of 
forces. It will, no doubt, be conceded that any particular beach 
can be defended if a sufficient garrison and suitable material are 
provided, but whether this method of defense is permissible as a 
general policy must depend upon the number of men required to 
secure all critical landing places and the relation of this number 
to the total number of available troops. 

13. Whether an extensive seacoast sector can actually be defended 
in this manner depends upon whether we can check landing at all 
favorable beaches and at the same time avoid the danger of an 
undue initial dispersion of available forces. If the entire force 
available is deployed as a cordon along the shore line the entire 
defense will break down as soon as the enemy has penetrated any 
part of the line. A successful defense must depend upon bringing 
up strong reserves in time to defeat the enemy before he can secure 
a solid footing at any part of the beach. 

It should be possible by means of wire entanglements and other 
obstacles placed at or near the water’s edge and covered by small- 
arms lire to cause delay and heavy losses to any landing party. Under 
such circumstances the enemy- will not be able to rush his covering 
detachments ashore on a broad front, and if the delay is sufficient to 
enable us to bring up adequate reserves we should be able to defeat 
him at the several points of penetration. The success of the defense 
must depend on the actual existence of these reserves, and this im¬ 
plies that a water-line defense, like any other defense, must depend 
upon having formed troops free to move to threatened points of the 
line. 

For example, if in a given seacoast sector 20,000 men are required 
as deployed detachments for the immediate defense of the shore 
line, and the total force available is only 20,000 men, the defense is 
weak, and must necessarily break down. But if means can be pro¬ 
vided through which 10,000 men can be relieved from the beach 
detachments and concentrated as supports and reserves, the chance 
of success is greatly increased. If this process can be still further 
continued, so that 5,000 men can form an efficient beach guard and 
leave 15,000 men in reserve, the prospects of a successful defense are 
still further increased. If these reserves are within easy marching 
distance of threatened points, or if they, can be brought up rapidly 
by rail or automobile from a greater distance, they should have some 
very decided advantages against an enemy who is still struggling to 
penetrate a fire-swept obstacle. 


44 JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 

Having in view, then, the defense of any given shore line, it would 
seem that success is to be secured by forming a sufficient initial 
resistance by means of shore detachments of minimum numerical 
strength, with the view of conserving the maximum number of men 
to be employed as supports and reserves. 

14. Under the contemplated system each beach considered favor¬ 
able for landing would be prepared for defense by providing fire- 
swept obstacles in the manner developed on the western front dur¬ 
ing the recent war; that is, wire entanglements or other suitable 
obstacles would be emplaced in such a manner as to check and retard 
the enemy from the moment that he attempts to leave his boats. 
Each of these entanglements would be covered by machine-gun bar¬ 
rages. Suitable small-caliber artillery would supplement these bar¬ 
rages, and would also fire on small boats as they come within range. 

Experience on the western front has shown that such a position 
can only be taken after careful preparation, involving the expendi¬ 
ture of large amounts of ammunition by highly specialized artillery, 
and then only when the actual assault is carefully organized in 
waves and is delivered as a surprise over a short distance from pre¬ 
pared parallels of departure and under the cover of carefully timed 
barrages. All of these essential conditions for success would be 
denied to an enemy who must advance to the position in small boats 
over several thousand yards of open water. 

If his ships were held at a distance by the fire of heavy mobile ar¬ 
tillery, he would be denied the necessary artillery preparation, be¬ 
cause the guns of his fleet would be unable to deliver the observed 
fire required for the destruction of widely scattered machine-gun 
nests. He could expect but slight relief from the preliminary de¬ 
struction of obstacles, as the attack of extensive belts of wire entangle¬ 
ment requires an accuracy of fire observation and an expenditure 
of ammunition that would probably not be within the capabilities of 
a fleet. He would probably be unprovided with or unable to make 
use of trench mortars and other special appliances recently developed 
for the attack of such positions. During his advance to the beach, 
his boats would come within the range of small and medium caliber 
guns that would suffer little from any counter battery effort from 
the fleet. Finally, on account of the extent and uncertainty of ranges 
and the flat trajectory of naval weapons, he would be denied any 
close artillery support at the moment of contact with his prepared 
enemy on the beach. 

15. The defensive system above outlined would require few, if 
any, permanent works to be constructed in time of peace. There 
would be ample time on the imminence of war for the works to be 
completed by the several sector garrisons assisted by civilian labor. 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 45 

Plans for the proposed works adapted to the requirements of each 
position as determined by careful reconnaissance should be prepared 
in peace and arrangements made for assuring the procurement of 
necessary material. The detailed reconnaissance of the position pre¬ 
liminary to the preparation of the plans will also determine the 
number of troops required for the initial garrison and the number 
and organization required for the local supports and reserves neces¬ 
sary for each position. The total number of reserves required for 
each coast defense sector as a whole w T ill depend upon the extent and 
configuration of the coastline, the number and extent of positions 
to be defended, and the general relation of railroads, tramways, 
highways, and other communications within the region. More or 
less isolated sectors like that centered on SanFrancisco would require 
a sufficient reserve to be practically independent of reenforcement. 
In closely connected sectors such as would be developed on the New 
England coast the sector reserves would be economized through the 
use of general strategic reserves for employment in any one of sev¬ 
eral adjoining sectors. While permanent works would not be re¬ 
quired in the beach positions, some peace-time development of roads 
and other communications might be necessary in certain areas. In 
many cases these communications and portions of the area in rear of 
the beach should be screened or camouflaged by means of trees or other 
vegetation. 

16. Referring to the map, the defense of the indicated coast-defense 
sector would be organized and developed as follows: 

On the imminence of war the troops allotted to the sector would 
be concentrated there and the several beach positions would be 
promptly prepared for defense. Upon the completion of this work 
all troops would be withdrawn to predetermined reserve positions, ex¬ 
cept the limited garrisons required to outpost the positions and to 
man the fixed machine guns and small cannon required for the beach 
barrages. Small patrols wnuld also be detailed for the observation 
of intervals of coast between the prepared positions. A complete 
system of signal communication throughout the sector would be in¬ 
stalled and arrangements made for the rapid transport of reserves 
to any threatened position by means of mechanical transport. The 
theory of the defense would be that the fire-swept obstacles at the 
beach could not be rushed by the enemy on a broad front, and that 
small bodies that might succeed in penetrating the beach defenses 
would be disposed of by local supports until stronger reenforce¬ 
ments could be forwarded from the reserves. 

17. The strength of the permanent beach cordon would be de¬ 
termined largely by the number of men required to man the fixed 


46 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 


machine guns and small and medium caliber cannon assigned to the 
beach position. By disposing the machine guns so that their fire will 
flank sections of beach they at once secure better protection and 
greater fire effect. Bearing in mind that .50-caliber machine guns 
can deliver an effective barrage up to 6,000 meters, it will be possible 
with 10 machine guns per mile to bring an effective barrage of more 
than 80 machine guns upon any wire entanglement within the po¬ 
sition. Each machine gun installed in a flanking position near the 
shore line will sweep the immediate beach with direct flanking fire 
and will be able to join in indirect fire barrages on more distant 
beaches. Machine guns firing at approaching small boats will have 
a great advantage in that the splash of the stream of bullets rises to 
a height of 15 or 20 feet and is a very conspicuous guide for accurate 
ranging. Allowing 10 machine guns and 4 small or medium caliber 
guns per mile, the personnel for serving them will not exceed 75 men 
for each mile of beach favorable for landings. This is ample, as it 
is assumed that no mobility will be required for these weapons and 
that a sufficient supply of ammunition will be kept at all times near 
the guns. With a total allowance of 150 men per mile there will be 
an ample force for manning these guns and providing local supports. 
This detachment will constitute the beach outpost and will furnish 
night patrols equipped with portable lights and flares. When the 
weather is favorable for landing operations small motor boats, pro¬ 
vided with rockets and other signal material, will extend the night 
reconnaissance to the front. 

18. The number of reserves required for a beach position will 
depend upon a great many factors that will be more or less variable 
in different sectors. However, a consideration of the probable de¬ 
velopment of the combat will throw some light on their employment 
and approximate number. The enemy on leaving his boats will 
immediately become involved in a difficult obstacle and will be 
exposed to a heavy machine-gun and shrapnel fire to which he can 
not reply. At the moment of landing he will be unsupported by 
artillery, and after traversing several thousand yards in boats it is 
hardly conceivable that he will be able to take a definite attack 
formation or to synchronize his attacks over any wide extent of 
beach. Under the circumstances, over considerable portions of the 
front his advance will be checked, and if he succeeds in passing the 
obstacle at all it will be by penetration on a narrow front by more 
or less disorganized columns. It will be the function of the small 
beach supports to meet the heads of these columns with the heavy 
fire of additional machine guns and automatic rifles or to counter¬ 
attack them, as the situation may require. In the preliminary or- 


47 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 


ganization of the position in depth the ground in rear of the beach 
will be prepared to facilitate communication for these supports to 
favor their fighting power in every way and to hamper and distract 
the advance of columns that succeed in penetrating the beach cordon. 
It is probable that tanks or other lighter and more mobile forms of 
armored cars will be used to great advantage with these beach 
supports. Under the circumstances, the enemy will be able to secure 
a footing only at the expense of heavy losses, and where he suc¬ 
ceeds it will take him some time to mop up and secure the ground 
gained and prepare his advance to a suitable covering position or 
preliminary base. In the meantime, formed reserves will concentrate 
on the area of penetration. These reserves will consist of infantry, 
machine-gun battalions, and light and medium artillery provided 
with mechanical transport capable of moving at a speed of 12 miles 
per hour. These reserves will move into a battle field prepared in 
advance for them and will act offensively. Assuming mechanical 
transport and a suitable system of roads, a properly organized re¬ 
serve detachment will be able to intervene within an hour and a half 
at any point of penetration on a beach front of 20 miles. Assuming 
this reserve to be one regiment of infantry with two additional 
machine-gun companies, one battalion of light artillery, and one 
battery of 155-millimeter howitzers, the number of combatant troops 
for a 20-mile beach position would be as follows: 


Beach cordon_1, 500 

Beach supports_1, 500 

Beach reserve: 

One regiment of infantry-•-3, 742 

Two machine-gun companies- 356 

One battalion light artillery- 780 

One battery medium howitzers or guns- 210 

8,088 • 

With this arrangement there would be a strong resistance to land¬ 
ing parties on the entire front, with a highly mobile reserve of 5,000 
men prepared to deal with the enemy at points of penetration. 

19. In the imaginary sector shown on the sketch map the entire 
front of the sector is 300 miles. The extent of beach indicated as 
favorable for landings and within striking distance of useful ob¬ 
jectives is about 70 miles. Under these conditions the combatant 
mobile troops required for the complete defense of the sector will be 
approximately as follows: 

Beach cordon_.- 250 

Beach supports- 2 ^° 

Beach reserves- 2 ^> ^52 

Total combatant mobile troops- 30,852 














48 JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 

The number of reserves allotted above would comprise four reserve 
detachments of the kind described in paragraph 18. They would be 
disposed along the roads so as to facilitate their prompt advance by 
mechanical transport. 

If a detailed joint study of the sector with the Navy should indi¬ 
cate that effective use of the minor harbors at 4 or 15 can be denied 
to the enemy by means of mine fields or other naval agencies, this 
would affect the importance of 4-5 and 13-14 as critical landing 
places and would result in a reduction in the number of troops 
required for the beach cordon and beach subposts. 

20. The feasibility of this method of defense depends upon the 
A following factors: 

(a) An enemy landing from boats on an open beach will con¬ 
sist largely of infantry without transportation, with 
limited ammunition and with no artillery except the 
smallest portable guns. Such a force has only a limited 
radius of action and must secure a favorable place for 
landing heavy materials, transportation, and reinforce¬ 
ments before it can engage successfully with a force 
of all arms. Until such an objective is reached and 
particularly at the moment of landing such a force will 
have but limited fighting power against a mobile force 
freely supported by suitable artillery. The landing 
force will, of course, receive certain support from the 
ships’ guns, but, when the situation demands it, this 
may be minimized by the appropriate use of fixed and 
railway artillery employed to hold the ships to a dis¬ 
tance from which effective artillery support will be 
impracticable. 

> (b) Our capacity to operate against detachments of this char¬ 
acter is greatly increased through the recent develop¬ 
ment of machine guns and entanglements for the beach 
defense and the great increase in the radius of action 
of mobile troops through the development of mechani¬ 
cal transport. 

(c) If we prepare to resist landings at all beaches within one 
day’s march of a favorable base or subbase, we can draw 
reserves from a distance of 100 miles before the enemy 
can secure his preliminary objective. This great de¬ 
velopment in the mobility of reserves makes possible a 
positive defense of all critical seacoast sectors without 
undue dispersion. 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 


49 


21. The applicability of the system to the coast line as a whole 
must depend upon detailed reconnaissance of all critical sectors and 
of all beaches favorable for landings. 

r 22. It is believed that this method of defense is particularly 
adapted to the defense of islands such as Oahu and that with a rea¬ 
sonable garrison landings can be positively prevented. By the same 
means landings within striking distance of the Panama Canal Zone 
also can be positively prevented. The positive defense of any naval 
base located on a small island such as Guam or Culebra is practicable 
in a similar manner. 

With all naval bases and all critical areas on our coast line secured 
in this manner, naval strategy will be completely freed from any 
purely defensive burden and the fleet will be able to concentrate all 
of its resources upon the campaign against the hostile navy. 

Under such a system the mobilization and expansion of our mili¬ 
tary forces can be developed in a deliberate and orderly manner 
without risk of invasion by any group of enemies, no matter how 
great* its naval preponderance may be. 

23. It is not to be understood that the beach defense outlined in 
this memorandum is proposed as sufficient in itself. It is proposed 
as the foundation of our coast-defense system, with which all other 
tactical resources should be coordinated. Among these other re¬ 
sources are the following: 

The Army system of coast defense should be constructed on the 
assumption that the battle fleet will no f participate in coast defense 
as such and that the defense should be complete and self-contained 
even if our fleet should lose command of the sea. Even under this 
assumption, however, certain naval agencies will be available and 
will exercise an important influence in the development of the project 
as a whole. 

Naval reconnaissance with its aerial observation and radio commu¬ 
nication will locate hostile naval forces at a great distance and will 
give timely warning as to their position and direction of motion. 
Seacoast submarines will dominate the coast line near certain naval 
bases and will greatly increase the difficulties of hostile convoys. 
This will influence the distribution and total number of troops re¬ 
quired for the beach cordon. In a similar way the approaches to 
certain otherwise practicable objectives may be completely barred by 
naval mine fields. Expert naval opinion as to effectiveness of the 
Army’s proposed system of defense against landings will be indis¬ 
pensable in the preparation of detailed plans. 

Field armies .—The defense against hostile landings outlined in 
this paper will require but a small part of the land forces of the 


50 


JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 


United States in time of war. After the coast defense forces are de¬ 
ployed, the remaining mobile forces will be formed into armies and 
employed as the plan for the particular war may demand. 

With a proper organization of our resources, a serious invasion of 
of the United States would be impracticable even for a hostile com¬ 
bination holding the command of the sea or both oceans. 

Movable heavy artillery .—In many cases movable high-power 
artillery will form an important auxiliary for the mobile detachments 
assigned to beach defense. Such weapons v T ill increase the difficulty 
of hostile landings by keeping hostile warships* at a distance from 
certain particularly favorable beaches. Artillery of this type should, 
however, be regarded purely as an auxiliary. Except as auxiliaries 
to mobile forces, they wdll have no conclusive influence on coast de¬ 
fense, and, on the other hand, mobile forces equipped with the usual 
field artillery types will generally be sufficient for the purposes of the 
defense even without the intervention of the heavier types. Another 
important role of these heavier weapons will be in the reenforcement 
of the armament of existing harbor defenses and as auxiliaries to the 
field army wherever siege operations may develop. 

Air forces .—The air forces will have an important function in 
seacoast reconnaissance. They w'ill also be able to attack hostile 
warships and transports, thus contributing to harbor defense and to 
coast defense as a whole. It is possible that they may also develop 
a capacity to convey supports at high speed to distant beach defense 
sectors. They should be able w T ith machine guns and bombs to take 
an effective part in the beach combat itself, especially at points of 
penetration and before other reserves can arrive. 

Chemical Warfare Service .—If gas remains a recognized military 
agency, it will frequentty be of decisive value in the beach defense. 

Tanks .—The probable use* of tanks and other armored cars as 
parts of the beach supports where the terrain is favorable has already 
been indicated. 

Cavalry .—With the resources of naval and aerial reconnaissance, 
and the development of mechanical transport for forwarding sup¬ 
ports and reserves, there wdll be but a limited role for cavalry in the 
proposed system of coast defense. 

While there are important fields of cooperation for all military 
agencies, it should be distinctly understood that a sound system of 
coast defense, except within the limits of the fixed harbor fortifica¬ 
tions, depends primarily upon the provision of mobile field forces; 
that the principal agencies for this defense are infantry with ma¬ 
chine guns, light and medium field artillery, and mechanical trans¬ 
port ; and that the roles of all other agencies and services should be 
considered strictly with reference to their subordinate capacities as 
highly useful but not indispensable auxiliaries. 


JOINT ARMY AND NAYY ACTION IN COAST DEFENSE. 51 

24. The positive defense against landings as proposed herein is 
simply a modern development of the “ First defense ” as proposed 
in the plans of the National Land Defense Board before the war. The 
effect of the development of fire-swept obstacles and mechanical 
transport on enormous scale has increased the fighting power and 
radius of action of u First defense ” troops to such an extent that 
they may now be employed in a more positive scheme of defense 
than was practicable when the original land defense plans were 
prepared. 


Part IV. 


DEFENSE PROJECTS AND PLANS (ARMY). 


1. In connection with the revision of existing defense projects and 
plans and the preparation by the Army of new defense projects and 
plans, and in order to secure uniformity in procedure the following 
compilation of decisions and policies of the War Department has 
been prepared in the War Plans Division, General Staff. The gen¬ 
eral direction and control of the development and execution of de¬ 
fense projects and plans by the War Department will be exercised as 
follows: 

(«) The War Plans Division, General Staff, is charged with cog¬ 
nizance of all matters involving new or modified defense projects and 
plans, and, in cooperation with the several divisions of the General 
Staff, in coordinating the action of the several services and agencies 
of the War Department in connection therewith. It shall also have 
the duty of originating consideration of such subjects when in its 
judgment necessary, and of recommending to the Chief of Staff 
whatever it considers essential to establish the sufficiency and effi¬ 
ciency of the defense of the continental United States and its over¬ 
sea possessions. 

(b) The War Plans Division, General Staff, will consider the sub¬ 
ject of national defense in its broadest sense, with the object of utiliz¬ 
ing all the means and elements available to accomplish the end in 
view. It will state the mission of each element and such general 
principles and instructions as will enable the elements involved to 
accomplish their specific missions. General instructions to tactical 
and territorial commanders concerned will issue from the War Plans 
Division on the authority of the Chief of Staff relative to details or 
development of approved defense projects or plans. Copies of such 
instructions will be furnished to the chiefs of War Department bu¬ 
reaus and services concerned. 

(c) Cooperation with the Navy in the different phases of develop¬ 
ment of defense projects and plans will be secured through the Joint 
Army and Navy Board and the Joint Army and Navy Planning 
Committee. 

(d) The chiefs of the several bureaus and services of the War De¬ 
partment will cooperate to the fullest extent in the execution of these 
instructions, and in the development of the technical duties of de¬ 
fense projects and plans. 

52 



JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 53 

2. The development and execution of defense projects and plans 
by territorial or tactical commanders will be governed by the fol¬ 
lowing : 

(a) The limits of defense sectors are prescribed from time to time 
by the War Department. As a general rule, the areas included in 
the several corps areas and overseas departments constitute defense 
sectors similarly named. For purposes of inspection, maneuvers, and 
tactical control, corps areas within the continental limits of the 
United States are grouped into Army areas. The Army area com¬ 
manders, when designated, are charged with the development and 
coordination of war plans and defense projects within their areas. 

(b) Corps area and department commanders become the “Sector 
commanders ” within the meaning of these instructions and as such 
are responsible for the defense of their respective sectors. The 
troops attached to each corps area or overseas department by the 
War Department constitute the forces available for the initial de¬ 
fense of the several sectors. 

( c ) Projects and plans relative to the defense of any sector will 
be developed, completed, and kept up to date by the responsible com¬ 
mander thereof. Every phase of this work pertains to functions 
for which the staff of every tactical or territorial unit is or should 
be at all times constituted and prepared to perform as one of its 
normal and most important duties. Therefore, throughout all 
phases of the work staffs will be expected to function normally and 
the formation of special boards or other agencies as substitutes for 
normal staff agencies or tactical command should not be resorted to. 
Any part of any staff may be increased by temporary detail without 
modification in its normal responsibility or functions. The officers 
selected for this important duty must be especially qualified for 
the work. If qualified officers are not available within the command, 
application should be made to the War Department for the detail 
of such officers. 

(d) Plans relative to subsectors will be prepared by the responsible 
tactical commanders thereof and after approval by the sector com¬ 
mander will constitute the plan for that particular subsector and 
will be included as such in the plant for the sector. 

( e ) Cooperation with the Navy will be secured through the com¬ 
mandants of the naval districts embraced in the limits of the sector. 
Responsible tactical and territorial commanders are authorized to 
confer directly with such commandants and will designate liaision 
officers whenever desirable. 

3. In order to avoid confusion and to establish uniformity in 
terminology the following will govern the use of certain terms or 
expressions: 

(a) A project is a tentative outline of construction and of procure¬ 
ment of means. It is necessarily presented in general terms, but 


54 JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 

nevertheless has in view the attainment of a definite result. Pro¬ 
jects are, therefore, indicative of policy and usually form the basis 
for estimates and legislation. The construction and procurement 
programs are later elaborated in more detail in connection with 
preparation of the plan of defense. For example, “Project for the 
defense of the Panama Canal.” Projects which have been approved 
by the Secretary of War become and are designated, “Approved pro¬ 
ject of the War Department for- 

(b) A flan is a formulated scheme for attaining some definite 
end and consists of a detailed and methodical arrangement of the 
means or successive steps believed to be necessary or conducive to 
attainment of the objects in view. Plans are based on approved 
projects of the War Department and on instructions of higher com¬ 
manders or of the War Department. Plans are prepared by respon¬ 
sible territorial and tactical commanders. For example, “ Plans for 
defense of Oahu, H. T.” 

(c) Coast defense includes dispositions and operations having for 
their object the meeting of a hostile attack made upon any portion 
of the seacoast of the continental United States, the Panama Canal, 
or the insular possessions. The elements that enter into coast de¬ 
fense comprise the naval forces, the harbor defenses, and the mobile 
forces of the Army. 

(d) Harbor defense includes dispositions and operations for the 
defense of a limited portion of the seacoast, ordinarily confined to 
important harbors. Such dispositions generally include fixed arma¬ 
ment and their accessories. The harbor defenses will be considered 
as units of fixed or sector artillery having definite missions over 
sea and land areas, and as such form an important part of the sector 
garrison. Pending preparation and approval of a project providing 
for the organization of harbor defense troops into units correspond¬ 
ing to battalions, regiments, and brigades, the principal harbor de¬ 
fense tactical unit requiring consideration under these instructions 
is the coast defense. The relation of coast defense commanders to 
the sector, subsector, and other commanders is the same as in the 
case of other commanders of tactical and combat units of the mobile 
forces of the Army. 

(e) Fixed armament includes guns, howitzers, and mortars mount¬ 
ed in fixed emplacements, incapable of being moved or readily trans¬ 
ferred and designed to fire over limited areas. 

(/) Mobile armament includes guns, howitzers, and mortars on 
movable mounts. The mobility possessed by armament of this class 
is subject to limitations and may be classified as strategical and tac¬ 
tical mobility. 

(g) Mobile forces of the Army include combat troops of all arms 
comprised in divisions, corps, and armies. 



JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 55 

( h) Defense sectors. —For command and other purposes the sea- 
coast areas are divided into sectors, which usually include defended 
and undefended areas. The limits of defense sectors are prescribed 
by the War Department. According to the foregoing, a defense 
sector comprises the entire sea frontier within its limits, of which 
the harbor defenses are strong points and not isolated points to be 
defended. A major sector is a sector of such magnitude as to require 
a sector reserve of a division or more and not susceptible of rein¬ 
forcement except from the general strategical reserve or by transfer 
from another sector. A minor sector is a sector of such magnitude 
that the sector reserve may be less than a division and yet so situ¬ 
ated as to make it inexpedient to organize it as a subsector. A minor 
sector is not susceptible of reinforcement except from the general 
strategical reserve or by a transfer from another sector. A sub¬ 
sector is a part of a major or minor sector , but forming a separate 
tactical command, with its own reserve, under the sector command 
and susceptible of reinforcement by the sector reserve. 

4. In the development of defense projects and plans the normal 
procedure will be as follows: 

(a) Instructions from the War Department directing the prepara- ' 
tion of a project or plan will, whenever practicable, state the mission 
to be assumed as a basis for the project or plan. The War Plans 
Division, in conjunction with Naval Operations, is studying and re¬ 
vising all the more important war plans. This will take a long 
time and until completed it will be impracticable to furnish corps 
area or department commanders (except in the case of Panama, Oahu, 
and the Philippines) definite missions, together with a statement of 
the forces they will have at their disposal and the necessary informa¬ 
tion as to the mission of adjoining commanders with whom they must 
cooperate. However, it is the desire of the War Department that 
each corps area or department commander study and revise his local 
plans of defense without waiting for the results of the War Plans 
Division work. In doing this, he will assume the more obvious and 
natural missions inherent in the location of his command and will 
assume the troops and material now at his disposal as available in the 
execution of such plans. 

(b) In working out these plans the corps area or department com¬ 
mander should carefully consider and apply, whenever practicable, 
the principles enunciated in W. P. D. Memorandum No. 1, entitled 
“A Positive System of Coast Defense.” This will necessitate a recon¬ 
naissance of the entire coast within the assigned limits with a view 
of classification as follows: 

(1) The location and extent of coast line which, for specified 
reasons, may be regarded as unfavorable for landing 
operations. 


56 JOINT ARMY AND NAVY ACTION IN COAST DEFENSE. 

(2) The location and extent of coast line considered favorable 

for landing operations, with the possible objectives and 
lines of advance in each case. 

(3) The beaches under (2), after consideration of the other 

elements of the problem, will be further classified into 
beaches where landings should be definitely resisted and 
beaches where, for specified reasons, arrangements for 
serious defense need not be provided. 

The corps area or department commander's study will undoubtedly 
show the necessity for certain increased numbers of troops, machine 
guns, artillery, permanent works, communications, reserve supplies, 
and additional storage facilities. The increases that are desired 
should be listed in order of priority, as to urgency, with results that 
will be obtained, if they are furnished, in such manner that the War 
Department can readily see that by furnishing certain of these items 
it can obtain a definite increased security to that portion of the coast. 
These various projects for employment of reinforcements, listed item 
by item and giving in each case the security that would result, would 
be such that if all were granted the corps area or department com¬ 
mander would be willing to acknowledge that with such means a 
positive system of coast defense would be obtained. 

( c) Five copies of the corps area or department project, prepared 
as abowe directed, together with necessary maps and estimates of 
funds required for the project, will be submitted to the War De¬ 
partment. 

( d) The project is then considered by the War Department and 
studied with a view of ascertaining if it fits into the general plans 
for national defense, and is approved in whole or in part or modi¬ 
fied according to circumstances. 

( e ) One copy of the approved project is returned to the sector 
commander, and the other four copies are filed in the several divi¬ 
sions of the General Staff. 

(/) The approved project is the basis for the development of the 
detailed plans which are kept on file at the headquarters of the 
tactical or territorial commander and subject to inspection by duly 
authorized representatives of the War Department. 

5. All defense projects and plans and papers pertaining thereto 
will be marked “ Secret ” and so considered. 

6. Nothing in the foregoing instructions should be construed as 
limiting the responsibility of chiefs of services or territorial or 
tactical commanders in initiating action relative to the sufficiency or 
efficiency of seacoast or harbor defenses as provided for in regula¬ 
tions. 


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